Fabrication rules based automated design and manufacturing system and method

ABSTRACT

An automated custom power supply design and manufacturing system uses an expert system containing a set of rules, including manufacturing limitations to limit design choices and ensure feasibility and manufacturability of the design. A design interface collects specifications from a user. A complement of power components for satisfying the electrical specifications is defined and mechanical specifications for each component are provided by the system for use in creating the mechanical design. After the mechanical design is established a thermal analysis is performed and the completed design is returned to a host computer. After an order is received, a computer integrated manufacturing system generates all of the specifications required to manufacture the components for the system and the system. 
     A multiconductor snake wiring system which uses a flexible bus structure with taps for providing connections to the components is also disclosed. An automated facility for manufacturing the snake wiring system is also described. A compact multilayer wiring structure for connecting the components and a unique process for manufacturing the wiring structure are also disclosed.

BACKGROUND OF THE INVENTION

This invention relates to automatically designing custom powerconverters.

Power converters accept power from an electrical input source andconvert it into a form suitable for use by electrical loads. One classof power conversion systems, called power supplies, are typically usedto convert power derived from a utility source, such as an AC utilityline or a DC telecommunications battery, into one or more regulated DCvoltages (e.g., 5 V, 12 V, 48 V) used for powering electronic circuitry.Specifications for a power supply are application specific. Thus, whilemany power supplies may share certain common characteristics such as asimilar input voltage range or the presence of a 5-volt output, manypower supplies are customized, by design, for use in a particularproduct or system.

Design of a custom power supply involves different skills and usuallytakes months to complete. For example, a typical custom power supplydesign may involve design of electronic power conversion circuitry;design, layout and procurement of printed circuit boards, packaging andcooling elements, source interface "front-end" circuitry (such as powerfactor correcting front-end circuitry or "auto-ranging" rectificationcircuitry for use with AC utility sources) and conducted EMI filtercomponents; fabrication of prototype assemblies; qualification andtesting of prototypes with respect to electrical, thermal, mechanicaland EMI/RFI specifications; and acquisition and submission of test datafor obtaining safety agency (e.g., Underwriters Laboratories, CanadianStandards Association) approvals. In addition, money and effort mustalso usually be invested in the development and qualification ofmanufacturing processes and equipment for each different custom powersupply.

Widespread commercial availability of high density power components suchas modular DC-DC power converters and related front-end power componentshelped simplify and shorten the custom power supply design cycle byeliminating the need to design, qualify and obtain agency approvals onpower conversion and front-end interface circuitry. However, weeks ormonths of effort are still often required to perform the packaging,thermal and other design and qualification tasks required to develop acustom power supply using power components.

General Electric Corporation has offered prepackaged modular buildingblocks for configuring switching power conversion circuits. Eachbuilding block (e.g., rectifier block, switch block, output filterblock) formed a portion of a switching power converter circuit and eachwas available in various voltage and current ratings to allowconfiguring supplies of different input voltage, output voltage, andpower ratings. A microcomputer-based software package aided the user inselecting those building blocks which, when connected together, wouldresult in a power converter which meets the user's functionalrequirements. The software selected those pre-defined blocks which wouldresult in a certain combination of input voltage, output voltage, andpower level.

Linear Technology Corporation, Milpitas, Calif., USA, has offered asoftware based power supply design program called SwitcherCAD; andNational Semiconductor Corporation, Santa Clara, Calif., USA, hasoffered a software based power supply design program called SimpleSwitcher. Both programs accept a set of predefined functionalspecifications and generate parts lists and schematics for a powerconversion circuit which meets the specifications. Both programs canproduce designs for different topologies (e.g., isolated flyback,non-isolated PWM buck). The user of the programs can modify componentvalues and other design parameters and observe the effects onperformance, e.g., conversion efficiency. Both programs use pre-definedequations for generating a solution.

Siemens has announced an expert system which runs on a personal computerfor aiding in the design of power supplies. It collects specificationsfor the power supply from the user, synthesizes possible structures, andreports the number of feasible solutions for the selected input/outputdescription. The price for a specified quantity and lot size arecalculated by the system. The configuration report is sent to themanufacturer's computer over a wide area network and then passed on tothe development department.

The manufacturer then designs the power supply. Circuit macros stored ina CAD system are called up, placed, and the clusters are connectedtogether to reduce development costs. The development time for designingthe power supply is typically four working days which is apparentlyperformed by the design engineers at the manufacturer.

SUMMARY OF THE INVENTION

In general, one aspect of the invention includes an automated powersupply design system for aiding a user to design a custom power supply.The design system includes an expert system having a rule. An interfacefor receiving power supply specifications from the user is provided. Acomponent definition system, having an input for receiving the powersupply specifications, generates a complement of components and providesmechanical parameters for the components. A mechanical layout system hasan input for receiving the mechanical parameters and an input forreceiving the power supply specifications and generates a mechanicaldesign of the custom power supply constrained by enforcing the rule.

Implementations of the invention may include one or more of thefollowing features.

An automated manufacturing specifications generator providesmanufacturing specifications needed by the manufacturing system tomanufacture the custom power supply. The automated manufacturingspecifications generator may additionally supply specifications for anyone or more of the following: manufacturing cables, a mounting plate,heatsinks, electrical power converter modules, or front-end assemblies,or for programming a programmable memory device with output controlinformation, for the custom power supply.

A computer integrated manufacturing ("CIM") facility includes at leastone fabrication station for manufacturing a component for the custompower supply. The CIM facility has an input for receiving componentspecifications comprising selected manufacturing specifications.

A production scheduler connected to receive the component specificationsallocates a time slot for production of the component by the CIMfacility.

A wiring station has an input for receiving interconnectionspecifications for fabricating interconnection components. Theinterconnection specifications may be for a circuit board and the wiringstation fabricates circuit boards or for a wiring harness and the wiringstation fabricates wiring harnesses. Additionally, the wiring harnessmay include a flat multi-conductor cable element and at least two tapelements and the interconnection specifications may include one or moreof the following: length and tap or fold and bend locationspecifications.

A heatsink station has an input for receiving heatsink specifications.The heatsink specifications may include machining instructions and theheatsink station may include machining equipment for fabricating aheatsink from metal stock. The heatsink specifications may includeposition information and instructions for selecting and installingprefabricated heatsink components.

The rule may include one or more of the following characteristics: (a) alimitation imposed by tooling restrictions of a manufacturing line, (b)a minimum component spacing limitation imposed to allow for wiringcomponents, or (c) a component orientation limitation.

The power supply specifications may include power supply inputspecifications and output specifications and the interface may acceptnumerical entries.

The interface may include a layout system in which component locationsmay be defined in a virtual space. The layout system may includecomponent icons representative of the complement of components. Theicons may be moved around the virtual space to define the componentlocations. The layout system may include a feature allowing the user tomanipulate the size or shape of the virtual space. The layout system mayinclude a drawing feature in which the system automatically adjusts thevirtual space to fit an arrangement of the component icons. Thearrangement may be created by the user. The layout system may include anautomatic arrangement feature in which the system automatically arrangesthe component icons and creates the virtual space to fit the arrangementof the component icons. The virtual space may comprise a flat surface orat least two separate flat surfaces. The component locations and thevirtual space may define the mechanical specifications for the custompower supply, including a mounting surface and mounting features.

The power supply specifications may include thermal specifications;safety agency specifications; information about the timing of turning onor off at least one output; information about the sequence for turningon or off at least two outputs; or information regarding one or more ofthe following: (a) an output voltage, (b) an output power, (c) a currentlimiting set point, (d) an over voltage set point, (e) output ripple,(f) input voltage range, or (g) a noise level. The power supplyspecifications may include power supply input specifications and outputspecifications and the interface may provide a list of choices for atleast one input specification. The list of choices may include buttonselectable options or a pull-down list of options.

The complement of components may include an electrical power convertermodule and the component definition system may generate an electricaldesign for the electrical power converter module. The componentdefinition system may also calculate an efficiency for the electricalpower converter module. The component definition system may generate anelectrical design which is optimized with respect to a optimizationparameter such as efficiency, reliability, or cost. Two or more of theoptimization parameters may be assigned relative weights and thecomponent definition system may generate the electrical designoptimizing the optimization parameters according to the assignedrelative weights.

The complement of components may include a plurality of electrical powerconverter modules and the component definition system may generate anelectrical design and provide an efficiency rating for each of theelectrical power converter modules. The system may calculate the totalinput power required by the electrical power converter modules using theefficiency ratings and the power output of the custom power supply, andselect circuitry for a front-end assembly. The system may calculate atotal power dissipation for the custom power supply and calculate atleast one heatsink dimension.

The system may provide feasibility information to the user regarding oneor more of the following conditions: (a) cooling requirements, (b)heatsink dimensions, (c) component orientation, (d) component spacing,(e) safety agency requirements, or (f) output orientation.

The custom power supply may include a user-defined package and the powersupply specifications may include at least one of the following details:(a) a shape of the user-defined package, (b) a dimension of theuser-defined package, (c) a position of at least one of the componentsin the user-defined package, (d) an orientation of at least one of thecomponents in the user-defined package.

The system may provide feasibility information to the user, includingacceptable relative locations and orientations for the components.

The rule may include one or more of the following: (a) safety agencyspecifications, (b) limitations imposed to allow two or more powerconverters to be connected into a load sharing array, or (c) thermalconstraints.

The complement of components may include electrical power convertermodules or a front end module.

In another general aspect, the invention includes an automated powersupply design system for aiding a user in designing a custom powersupply. An expert system includes a rule representing limitationsimposed by a manufacturing system. An interface is provided forreceiving power supply specifications from the user. A componentdefinition system, having an input for receiving the power supplyspecifications, generates a complement of components based upon thepower supply specifications. The power supply design system constrains,to an acceptable range, the power supply specifications by enforcing therule and generates a custom power supply design for the custom powersupply. An automated manufacturing specifications generator, having aninput for receiving the custom power supply design, suppliesmanufacturing specifications needed by the manufacturing system tomanufacture the custom power supply.

In another general aspect, the invention includes a method for aiding auser to design a custom power supply. A rule representing limitationsimposed by a manufacturing system is defined. Specifications arereceived from the user and a complement of components is generated.Mechanical parameters for the components are provided and mechanicaldesign information is collected from the user. The range of acceptableinputs for the specifications or the mechanical design information isconstrained by enforcing the rule.

Implementations of the invention may include one or more of thefollowing features.

Manufacturing specifications needed by the manufacturing system tomanufacture the custom power supply may be generated. The specificationsmay include one or more of the following: (a) specifications formanufacturing cables for the custom power supply, (b) specifications formanufacturing a mounting plate for the custom power supply, (c)specifications for manufacturing heatsinks for the custom power supply,(d) specifications for manufacturing electrical power converter modulesfor the custom power supply, (e) specifications for manufacturingfront-end assemblies for the custom power supply, or (f) specificationsfor programming a programmable memory device with output controlinformation.

A custom power supply design may be provided to a computer integratedmanufacturing ("CIM") facility. The CIM may include at least onefabrication station for automatically manufacturing a component for thecustom power supply. A time slot may be allocated for production of thecomponent by the CIM facility.

Interconnection specifications may be provided to the CIM facility forfabrication of interconnection components. The interconnectionspecifications may be circuit board specifications for fabrication of acircuit board by the CIM facility or wiring harness specifications forfabrication of a wiring harness by the CIM facility. The interconnectionspecifications may include at least a length and a tap locationspecification and the wiring harness may comprise a flat multi-conductorcable element and a tap element. The interconnection specifications mayalso include a fold or bend location specification.

Heatsink specifications may be provided to the CIM facility forfabrication of a heatsink. The heatsink specifications may includeautomatic machining instructions for fabricating a heatsink from metalstock or position information and instructions for selecting andinstalling prefabricated heatsink components.

The rule may include one or more of the following characteristics: (a) alimitation imposed by tooling restrictions of a manufacturing line, (b)a minimum component spacing limitation imposed to allow for wiringcomponents, or (c) a component orientation limitation.

Numerical entries may be received from the user and the specificationsmay include power supply input and output specifications.

A layout system allowing component locations to be defined within avirtual space may be provided. Component icons representative of thecomplement of components may also be provided and the user may beallowed to move the icons in the virtual space to define the componentlocations. The size or shape of the virtual space may be allowed to bemanipulated. The virtual space may be automatically adjusted to fit anarrangement of the component icons. The arrangement may be created bythe user. The component locations may be automatically arranged and thevirtual space adjusted to fit the arrangement. The virtual space mayinclude a representation of a flat surface or a representation of atleast two separate flat surfaces. The component locations and thevirtual space may define the mechanical specifications for the custompower supply, including a mounting surface and mounting features.

The specifications may include thermal specifications; safety agencyspecifications; information about the timing of turning on or off atleast one output; information about the sequence for turning on or offat least two outputs; or information regarding one or more of thefollowing: (a) an output voltage, (b) an output power, (c) a currentlimiting set point, (d) an over voltage set point, (e) output ripple,(f) output input voltage range, or (g) a noise level.

A list of choices may be provided for selection by the user and thespecifications may include power supply input specifications and outputspecifications. The list of choices may include button selectableoptions or a pull-down list of options.

The complement of components may include an electrical power convertermodule and an electrical design for the electrical power convertermodule may be generated. An efficiency may be calculated for theelectrical power converter module. The electrical design may beoptimized with respect to an optimization parameter such as efficiency,reliability, or cost. The optimizing may include assigning relativeweights to two or more of the optimization parameters and carrying outthe optimizing according to the assigned relative weights.

The complement of components may include a plurality of electrical powerconverter modules. An electrical design for each of the electrical powerconverter modules may be generated, an efficiency rating for each of theelectrical power converter modules may be provided, the total inputpower required by the electrical power converter modules may becalculated using the efficiency ratings and the power output of thecustom power supply, and circuitry for a front-end assembly may beselected.

The total power dissipation of the custom power supply and at least oneheatsink dimension may be calculated.

Feasibility information may be provided to the user regarding one ormore of the following conditions: (a) cooling requirements, (b) heatsinkdimensions, (c) component orientation, (d) component spacing, (e) safetyagency requirements, or (f) output orientation.

The custom power supply may include a user-defined package and thespecifications may include one or more of the following details: (a) ashape of, (b) a dimension of, (c) a position of at least one of thecomponents in, or (d) an orientation of at least one of the componentsin, the user-defined package.

Feasibility information may be provided to the user regarding acceptablerelative locations and orientations for the components.

The rules may include one or more of the following: (a) safety agencyspecifications, (b) limitations imposed to allow two or more powerconverters to be connected into a load sharing array, or (c) thermalconstraints.

In another general aspect, the invention includes a method for aiding auser to design a custom power supply. A rule representing limitationsimposed by a manufacturing system is defined. Specifications arereceived from the user and a complement of components is generated basedupon the specifications. Manufacturing specifications needed by themanufacturing system to manufacture the custom power supply aregenerated.

In another general aspect, the invention includes a capacitor assemblyfor use with a power supply. The assembly includes a capacitor, a wiringharness electrically connected to the capacitor and adapted forelectrical connection with the power supply, and a mounting assembly.The mounting assembly mechanically supports the capacitor and is adaptedto allow the capacitor assembly to be thermally decoupled from the powersupply.

In another general aspect of the invention a power supply includes aplurality of heat dissipative components and a capacitor assemblyadapted for electrical connection with the power supply. The capacitorassembly is adapted for mounting separate from the heat dissipativecomponents in an environment thermally remote from the heat dissipativecomponents.

In another general aspect of the invention, a power supply, includes aplurality of electrical power converter modules and a flatmulticonductor cable. The cable includes a control line for eachelectrical power converter module, a power distribution line, and anauxiliary conductor for connecting adjacent modules in a load sharingarray. The auxiliary conductor includes at least one discontinuity tointerrupt electrical connection between adjacent electrical powerconverter modules which are not members of the same load sharing array.

In one general aspect of the invention, a wiring harness includes a flatcable with a plurality of separate conductors covered with insulatingmaterial. A cable tap including a tap conductor has a first portionlying in a plane parallel to the cable at a selected tap location on thecable. A tap connection includes a tap opening in the insulatingmaterial of the cable at the tap location exposing a tap area of aselected conductor of the plurality of conductors and an electricalconnection formed between the tap conductor and the selected conductorat the tap area.

Implementations of the invention may include one or more of thefollowing features. Laser ablatable insulation may be provided on atleast one side of the cable for removal by laser ablation equipment. Thelaser ablatable insulation may be a polyester film. The tap may furtherinclude a tap fold which is folded perpendicular to the cable. The tapfold may be made along an axis parallel to the length of the cable.

The flat cable may include a cable bend along an axis perpendicular tothe cable. A cable fold having an axis parallel to the length of thecable may also be provided. A dimple may be disposed in the cable tofacilitate forming the cable fold. The dimple may be locatedsubstantially along a centerline of the cable prior to formation of thefold.

The taps may include a second portion having a conductive pad which iselectrically connected to the tap conductor and provides a connectionarea for mating with an electrical terminal. The connecting area mayinclude a hole for mating with a terminal pin on an electrical powerconverter module. The connecting area may include an area to mate with acircuit board.

The cable may include a bend having an axis perpendicular to the cablefor snaking around or between components.

The plurality of conductors may include a power conductor and a signalconductor. The power conductor has a higher current carrying capacitythan the signal conductor.

The wiring harness may include a mechanical bond between the tap and thecable.

A power tap having a power tap conductor has a current carrying capacitylarger than the tap conductor. A power tap connection includes a powertap opening in the insulating material of the cable at the power taplocation exposing a power tap area of the power conductor. An electricalpower connection is formed between the power tap conductor and theselected power conductor through the opening. The power tap areacomprises an area which is greater than the tap area. The power tapopening may include a plurality of openings and the electrical powerconnection may include a plurality of connections.

A front end connection includes at least one power tap for connecting toa power conductor and at least one tap for connecting to a signalconductor. Two or more module connections have a power tap forconnecting to a power conductor and a tap for connecting to a signalconductor.

A selected conductor may have a discontinuity dividing the selectedconductor along its length.

A plurality of signal conductors and a plurality of power conductors maybe provided. The front end connection may include a respective tap foreach of the conductors and a respective power tap for each of the powerconductors. The module connections may include a tap for connecting tothe selected conductor.

In another general aspect of the invention, a method of interconnectingcomponents includes providing a flat multiconductor cable having aplurality of conductors covered with insulation. A section of the cableis cut to have a predetermined length. A portion of insulation from apreselected area is removed to expose a preselected one of theconductors. An electrical tap having a tap conductor is provided. Thetap is positioned on the preselected area and the tap conductor iselectrically connected to the preselected conductor.

Implementations of the invention may include one or more of thefollowing features. Laser ablation may be used to remove the insulation.A bonding agent may be applied to the cable in an area around thepreselected area for mechanically securing the tap to the cable. Aninsulating layer may be applied to cover the preselected area. The cablemay be folded along an axis aligned with the length of the cable. Thecable may be bent along an axis perpendicular to the length of thecable. A discontinuity may be formed in a preselected one of theplurality of conductors. The cable may include a plurality of controlconductors and at least two power distribution conductors. Theelectrical connection may be formed by soldering.

In another general aspect of the invention, a electrical apparatusincludes two or more component modules, each occupying a respectivevolume having respective overall height, width, and length dimensions,and at least two electrical connection terminals. A planarinterconnection structure has a first and a second conductive layerseparated by insulation. The planar structure is adapted for makingconnection to the electrical connection terminals of each componentmodule and for lying in a space along an edge of the respective volumewithin the overall height dimension and without being located adjacentto more than three sides of each module. The planar structure provideselectrical connections between the electrical connection terminals.

Implementations of the invention may include one or more of thefollowing features. The planar interconnect structure may includecircuit board material having a conductive layer which is cut and routedin the fashion of a point-to-point wire cable. The modules may have anindentation and the planar structure may have a width adapted to fitwithin the indentation. The electrical connection terminal may include apin having a portion generally perpendicular to the board at aconnection point. A hole for accepting the pin and a conductive eyeletin the hole and electrically connected to the first conductive layer maybe provided for making electrical connection to the pin. An insulativesleeve may be used to provide insulation between the eyelet and thesecond conductive layer. The first and second conductive layers maycomprise power conductors. A third conductive layer is separated fromthe first conductive layer by insulation and includes at least twosignal lines formed by removing conductive material from the thirdconductive layer. Jumper landings make electrical connection between aselected one of the connection terminals and a selected one of thesignal lines.

A cable having a plurality of signal conductors may also be provided.The cable may be held in a position substantially perpendicular to theboard. A connection bracket includes a contact for engaging a selectedone of the connection terminals, a flat cable supporting surface formaintaining the cable in position, and a selective cable connectionportion for selectively connecting to a selected one of the plurality ofconductors. At least one of the signal lines may include a discontinuitybetween modules.

In another general aspect of the invention, a method of interconnectingcomponents includes providing a flat multilayer laminate having aplurality of conductive layers separated by insulation. A section of thelaminate is cut to have a predetermined shape. Portions of an exposedone of the conductive layers is removed by machining to form a pluralityof conductive traces. A hole is machined in the laminate to form aconnection to a preselected one of the conductive layers. The hole has afirst width in the preselected layer and a second larger width in theother conductive layers. A conductive eyelet is inserted into the holefor making contact with the preselected one of the conductive layers.

Implementations of the invention may include one or more of thefollowing features. An insulative sleeve is provided in the hole forinsulating the eyelet from at least one of the other conductive layers.At least two jumper landings are formed and a jumper is soldered to forma connection between the landings or a conductive layer is pad printedto form a connection between the jumper landings. An insulative layermay be pad printed over the laminate in an area between the jumperlandings before the conductive layer is pad printed. A discontinuity maybe formed in a preselected one of the plurality of conductors. Thelaminate may include a top conductive layer for forming signal lines andat least two interior conductive layers for distributing power. One endof the eyelet may be clinched after it is positioned in the hole.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of three package styles for modular powerconverters.

FIG. 2A is an exploded, perspective drawing of a power supply assembly.

FIG. 2B is a schematic block diagram of a power supply system.

FIG. 3A and FIG. 3B show the power supply assembly of FIG. 2A with aunitary finned heat sink.

FIG. 4 shows the power supply assembly of FIG. 2A with multiple heatsinks.

FIG. 5 is a block diagram of a computer aided design system.

FIG. 6 is a block diagram of a manufacturing system.

FIGS. 7A through 7H show sample data entry display screens.

FIG. 8 is a block diagram of a power supply design process.

FIG. 9 shows a portion of the power supply assembly.

FIGS. 10A and 10B show side and end views of a length of cable.

FIG. 11 shows a front-end power tap for use with the cable of FIG. 10.

FIG. 12 shows a front-end signal tap for use with the cable of FIG. 10.

FIG. 13 shows a maxi/mini-module power and signal tap for use with thecable of FIG. 10.

FIG. 14 shows a micro-module power and signal tap for use with the cableof FIG. 10.

FIG. 15 shows a fabrication line for assembling a length of cable of thekind shown in FIGS. 9 and 10.

FIG. 16 shows a step in the assembly of the cable of FIG. 9.

FIG. 17 shows another step in the assembly of the cable of FIG. 9.

FIG. 18 shows another step in the assembly of the cable of FIG. 9.

FIG. 19 is a schematic block diagram of a two plate power system.

FIGS. 20A though 20D show power factor correcting front-end assemblies.

FIGS. 21A through 21H show capacitor assemblies.

FIGS. 22A through 22D show auto-ranging front-end assemblies.

FIG. 23 shows a sample finite element analysis of a heatsink.

FIG. 24 shows a sample computer-integrated-manufacturing area forassembling the power supplies.

FIG. 25 shows a portion of a power supply assembly with a section of asnake circuit board interconnect.

FIG. 26 is a top view of a section of a snake circuit board.

FIG. 27 is a top view of the snake circuit board with jumpers installed.

FIG. 28 is a cross-sectional perspective view of a snake circuit boardand a converter module.

FIG. 28A is a cross-sectional side view of a snake circuit board on aconverter module.

FIG. 29 is an expanded cross-section of a connection to the V- powerconductor on the snake circuit board.

FIG. 30 is an expanded cross-section of a connection to the V+ powerconductor on the snake circuit board.

FIG. 31 shows a portion of a power supply assembly with a section of asnake circuit board interconnect.

FIGS. 32A, 32B, and 32C are a perspective, side, and top view of ahybrid snake cable and circuit board interconnection system with aconverter module.

FIGS. 33A, 33B, and 33C are cross-sectional drawings of a portion of asnake circuit board.

FIGS. 34A and 34B perspective and top views of a milling bit routing aconnection hole in a snake circuit board.

FIGS. 35A and 35B are top views of minimum width and maximum width snakecircuit board solutions for a power system layout.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, high density, modular DC-DC converters areavailable in a wide variety of input voltage, output voltage and powerlevels. For example, three different styles of power converter modulesmicro 10, mini 20, and maxi 30 (corresponding, for example, to the 700,800, and 900 Series of DC-DC converters manufactured by VicorCorporation, Andover, Mass., USA) are shown in FIG. 1. For a givencombination of input and output voltage ratings (e.g., 48 V nominalinput, 5 V output; or 300 V nominal input, 48 V output), the maximumamount of power which can be delivered by a power converter module in aparticular package is related to the package size. A converter module inpackage style 10 might be rated to deliver up to 150 Watts of outputpower at a baseplate 5 temperature rating of 100 degrees Celsius forexample. Similarly, converter modules in package styles 20 and 30 mightbe respectively rated to deliver up to 250 and 600 Watts of output powerat the same 100 degrees C baseplate temperature.

The power delivered to a single load can be increased by operating twoor more converter modules in a power-sharing array as disclosed incommonly assigned U.S. Pat. No. 4,648,020, entitled "Power BoosterSwitching at Zero Current" and U.S. Pat. No. 5,079,686, entitled"Enhancement-Mode Zero-Current Switching Converter" both incorporatedhere by reference. A virtually limitless number of custom power suppliesmay be configured using combinations of different quantities and modelsof converter modules of the kind shown in FIG. 1.

One embodiment of a power supply assembly 40 comprising modular DC-DCpower converters and other related modular power conversion componentsis physically depicted in FIG. 2A and schematically depicted in FIG. 2B.Referring to FIGS. 2A and 2B, three DC-DC converters 20a, 20b, 30a areshown in perspective above a flat top mounting surface 82 of a metalmounting plate 80. Also shown are "front-end" modules 50 and 55. Theterm "front-end" refers generally to circuitry which is connectedbetween the externally supplied power supply input source(s), such asthe AC utility line or DC telecommunications battery, and the inputs ofthe DC-DC converter modules 20a, 20b, 30a. Front-end module 50 containsconducted electromagnetic interference ("EMI") filtering elements whilemodule 55 contains AC-to-DC conversion circuitry. A power source, suchas the AC utility line voltage, is fed into the EMI filter module 50 viapower connector 60. The EMI filter module 50 attenuates electrical noisegenerated by the AC-to-DC converter module 55 and the DC-DC converters20a, 20b, 30a, and allows the assembly 40 to meet limits on the amountof EMI fedback to the power source. Traces (not shown) on the front-endprinted circuit board ("PCB") 70 connect the input pins 51 of the EMIfilter module 50 to the input power connector 60. The AC voltage,delivered at the output pins 52 of the EMI module 50, is fed to theinput pins 56 of the AC-to-DC converter module 55 by traces (not shown)on PCB 70. The DC output of the AC-DC module is delivered to output pins57. Control signals may also be delivered by the AC-DC module at pins58. For example, signals for controlling the turn-on during power-up andturn-off during power-down of the DC-DC converters 20a, 20b, 30a, may beprovided at pins 58.

Referring to FIG. 2B, a microprocessor control unit ("MCU") 75 may alsobe incorporated into the front-end board 70. The MCU 75 may be a simpleprogrammable microcontroller such as the PIC16C711, manufactured byMicrochip Technology Inc., 2355 West Chandler Blvd., Chandler, Ariz.,U.S.A. which can be programmed to control the sequence of and relativetiming for turning on and turning off the outputs in the power system40. The MCU 75 receives the control signals from pins 58 of the AC-DCmodule 55 as inputs. Control signals 76 delivered from the MCU to theindividual modules are also shown in FIG. 2B. The MCU may be programmedto automatically turn on selected outputs, or combinations of outputs,in a predetermined order when the system is powered up and to shut downselected outputs in a predetermined order when the system is powereddown (e.g., during a brown-out or in the event of some other failurecondition). A control interface through which an external system mayinterrogate the MCU to receive the status of the power system and alsoissue control signals to the power system (e.g., for turning converteroutputs on and off under control of the external source) may also beprovided on connector 62.

Each MCU may provide, several control signals 76, each of which may beused to control one or more outputs (each output being provided byeither a single converter module or by a power-sharing array of two ormore modules). Another control signal line 77 (FIG. 2B) may also beprovided for arranging sets of adjacent converters into power-sharingarrays. The control signal lines are provided by means of an automatedwiring system described below.

The power system 40 may comprise several, e.g., up to three, mountingplates 80 each having up to six control lines. The sub-system on eachplate is referred to as a power processing unit ("PPU"). One example ofa two-plate power system is schematically shown in FIG. 19. Each PPUincludes its own MCU. One computer interface 62 is provided by a mainMCU which then communicates with additional MCUs through connector 63.The MCUs on the other PPU front-end boards function as remote MCUs.During the power-up and power-down sequencing and the brown out control,the master MCU issues commands to the remote MCUs via the controlinterface 63. Power is provided to the remote PPUs via power connector61. A two PPU power system is shown schematically in FIG. 19. In thefigure the main PPU 41 is shown connected to the remote PPU 42. Notethat the remote PPU may have a simplified front-end circuit.

One way of connecting DC input power and control signal lines to theconverter modules is to provide several sets of interconnect pads 25,26, 27 along the periphery of PCB 70 as shown in FIG. 2A. The DC powerfrom the AC-DC converter module 55 is delivered by traces (not shown) topads a, d at each set of interconnect pads 25, 26, 27; and controlsignals from the MCU 75 are delivered by traces (not shown) to pads b, cat each set of interconnect pads 25, 26, 27. The DC voltage (a, d) andcontrol signal (b, c) input pins 22, 21, 31 of each DC-DC convertermodule 20a, 20b, 30a may be directly connected to the DC voltage andcontrol signals at their respective set of interconnect pads 26, 27, 25on PCB 70. Using this approach, however, a different PCB 70 must beprovided for each different power system 40 in order to interface todiffering numbers and locations of converters. Alternatively, a wiringharness may connect each converter to its respective interconnect pads.Another, more flexible, method for interconnecting converters with astandardized front end PCB 70 assemblies is described below and shown inFIG. 9.

The front-end PCB 70 and all of the parts connected to it (e.g., EMI andAC/DC modules, connectors, MCU, and related circuitry) will be referredto below as the "front-end". In general, there may be several differentkinds of front-ends (e.g., a power-factor correcting front-end; anauto-ranging, capacitively filtered rectifier front-end; or a DC inputfront-end).

To minimize the overall height of the front end assembly, the uppersurfaces 50a, 55a (FIG. 2A) of modules 50, 55 are arranged to protrudethrough openings 50b, 55b in the PCB 70 (as described in commonlyassigned U.S. Pat. No. 5,365,403, entitled "Packaging ElectricalComponents," which is incorporated here by reference). The front-end andpower converter modules may be firmly mounted to plate 80 using screws(e.g., screw 89) which pass through holes or slots 87 in the flanges ofthe module baseplates 5 (FIG. 1) into tapped holes 87a in plate 80.

In the power supply 40 of FIG. 2A, the front-end AC-DC converter module55 may be made a power-factor correcting module ("PFC module"). A PFCmodule presents an essentially unity power factor load to the AC utilitysource while delivering a regulated DC output voltage to the inputs ofall of the DC-DC converters 20a, 20b, 30a. Alternatively, module 55 mayinclude front-end circuitry to perform conventional rectification of theAC input and provide input surge current limiting. In either case, theoutput filter capacitors which are typically used at the output of theAC-DC converter module 55 may be provided in a separate capacitorassembly (called the "HUB") 92 as shown in FIG. 2A. One advantage ofphysically separating the filter capacitors from the power supplyassembly 40 is that it allows the overall height of the power supply 40to be minimized. Another advantage is that the HUB 92 is thermallydecoupled from the relatively high operating temperatures of the powersupply 40 assembly. Since mean time before failure ("MTBF") and physicalvolume of electrolytic capacitors typically used for such filteringapplications are temperature dependent, this allows for a reduction incapacitor size and improvement in capacitor MTBF. Another advantage isthat the customer may change the amount of capacitance after the powersupply 40 is manufactured thereby changing certain operatingcharacteristics such as the ride-through and hold-up times. Inconventional power supplies where the capacitors are typically mountedon a printed circuit board, the capacitance is fixed because the printedcircuit board is designed to accept a fixed number of capacitors of aparticular size. The HUB 92 is connected to the output pins 57 of theAC-DC converter by means of cable 66 and connector 64 and traces (notshown) on PCB 70. The length of cable 66 may be specified by thecustomer.

For DC input power supplies, the front-end may include an EMI filtermodule and in-rush and monitoring circuitry as well as surge protection.Heavier gauge cabling and PCB traces may be used to accommodate highercurrent flows and the AC-DC module 55 is omitted in the DC inputfront-end.

The structure illustrated in FIG. 2A can be adapted to a wide variety ofpower supply designs. The complement of output voltages, and the totalpower delivered by each output, can be altered by selecting anappropriate combination of DC-DC converters and front-end assembly. Forexample, in one embodiment of a power supply assembly 40, two converters20a, 20b (FIG. 2B) might form a power sharing array which might delivera total of 500 Watts at an output voltage of 15 Volts and converter 30amight deliver 5 Volts at 80 Amperes. Thus, the power supply mightdeliver a total of 900 Watts from two independent, regulated outputs.

The output pins of the DC-DC converters may be connected to loads (notshown) and other external devices via connectors 90. The output pins mayinclude power output pins and output trim and control pins such as pins34 and 34a respectively. The connectors 90 may be of the kind describedin Nowak, et al, U.S. patent application Ser. No. 08/744,110, entitled"Connector," filed Nov. 5, 1996. The physical positioning of thedifferent outputs, relative to each other and to the peripheral edges ofthe plate 81a, 81b, 81c, may be established by appropriately choosingpositions for the converters 20a, 20b, 30a on the top surface 82 of theplate 80.

One way to provide heat sinking for the assembly 40 of FIG. 2A is to putfins 85 on some or all of the entire rear surface 83 of the mountingplate 80, as shown in FIG. 3A. A separate heat sink assembly 93 may beattached to the rear surface 83 of the heat sink plate 80, as shown inFIG. 3B. Alternatively, an integral heatsink and mounting plate may befabricated by starting with a plate 80 of suitable thickness andmachining fins 85 to the desired thickness and height. Alternatively, anintegral heatsink and mounting plate may be fabricated from extrudedheatsink stock. The size of the plate 80 and the thermal loss in thepower supply 40 will vary from design to design. The heat sinkingapproach of FIGS. 3A and 3B therefore requires a wide range ofcustomization because each power supply assembly will present its uniqueheat sink requirements.

Another way to provide heat sinking for the assembly 40 is illustratedin FIG. 4. Individual heat sinks 86a, 86b, 86c, 86d, and 86e are mountedon the rear surface 83 of the mounting plate 80 in positionscorresponding to the locations 88a, 88b, 88c, 88d, and 88e of theconverter modules on the top mounting surface 82 of the plate 80. Asshown in FIG. 4, the outlines of the individual heatsinks on surface 83match the outlines of the converter module baseplates (shown as dashedlines as 88a-88e) on the front surface 82.

One advantage of providing individual heat sinks as illustrated in FIG.4 is that customized heatsinking of a wide variety of power supplyassemblies 40 may be provided using a few standardized heat sinks. Eachstandardized heatsink is made to conform to the baseplate layout of aparticular module size, e.g., micro, mini, and maxi as shown in FIG. 1.Since the heat sources are concentrated in the modules, locating finnedheat sinks directly at the mounting locations 88 of the modules providesvery little loss in cooling effectiveness relative to that provided byfins over the entire surface 83 (FIG. 3a). Alternatively where finheight is a concern, the individual heatsinks may be made to occupy agreater area than that of the baseplate while still conforming to themounting holes of the converter module baseplates.

Mounting hardware used to mount the converters to the front surface 82may also be used to mount the heat sinks 86a-86e to the rear surface 83.For example, a screw 89 may pass through a hole 87 (FIG. 2A) in theflange of the module baseplate 5; pass through a hole in the mountingplate 87b (FIG. 4); and be threaded into a tapped hole 94 in the heatsink. Alternatively, the screw 89 could pass through a hole 94 in theheat sink and be threaded into a nut 95 as shown in FIG. 4. Thus anotherbenefit of the method of FIG. 4 is that the same set of hardware andholes may be used for mounting the modules and the heat sinks.

A scheme for electrically connecting virtually any combination ofconverter modules to a standardized front end assembly is shown in FIG.9. In the Figure, a snake cable assembly 480 carries power and controlsignals from a front-end PCB 70 to converter modules 10b, 20b, 30b (forclarity, front-end components, such as front-end modules, connectors,MCU, and other components, are not shown in FIG. 9).

Converter module input voltage is delivered at pins 72a and 72b onfront-end PCB 70. Pins 72a are positive polarity; pins 72b are negativepolarity. Likewise, five control signals are delivered to pins 74athrough 74e on PCB 70. Input voltage and control signals are routed tocable 400 by front-end power tap 440 and front-end control signal tap450 and are routed from the cable 400 to individual converter modules10b, 20b, 30b by module taps 470, 460a, and 460b. One set of power andcontrol pins 72, 74 on front-end PCB 70 are used to connect to all ofthe converter modules on a PPU.

As shown in FIGS. 10A and 10B, the cable 400 includes power conductors410, 420 and control conductors 431-436. The conductors are sandwichedbetween flexible insulating films (e.g., Kapton polyamide insulatingfilm or polyester film). Power conductors 410, 420 are sized to carry DCpower to the inputs of the converter modules 10b, 20b, 30b withacceptable power losses. For low voltage, DC input power supplies, e.g.,48 V and lower, power conductors 410, 420 can be made bigger, to keepdistribution losses manageable.

A reference linear dimple 405 runs along the length of the cable, asshown in FIG. 10B. The reference dimple 405 aids in properly folding thecable 400 after the power, control signal, and module taps areconnected. The dimple 405 may also be used as a position reference whileplacing and assembling the taps onto the cable provided that the dimplelocation is maintained within acceptable tolerances during manufacture.

Referring to FIG. 11, a front-end power tap 440 for making a connectionbetween the power conductors 410, 420 of the snake cable and thefront-end DC output (at pins 72a, 72b) is shown. Two plated conductors441, 442 are arranged between layers of flexible, insulating, film.Portions of the respective conductors are exposed at selected areas toallow contact to be made. Exposed pads 443 and 444 on the power tap 440facilitate contact with the power conductors 410 and 420 of cable 400,respectively. Holes 445 and 446 are for connecting to pins 72a, 72b onthe front-end PCB.

Referring to FIG. 12, a front-end control signal tap 450 is shown formaking connections between the control conductors 431-435 and thecontrol signal pins 74a-74e on the front-end PCB 70. The front-endcontrol signal and power taps differ in the number of connections whichare made, but are otherwise similar in construction. Plated conductors451 through 455 are arranged between layers of flexible, insulating,film. Insulation is removed to expose areas to which connections are tobe made (e.g., exposed pads 457 allow connection to conductors 431-436on cable 400 and exposed pads with holes 456 allow connection to controlsignal pins on the front-end PCB 70).

FIGS. 13 and 14 show, respectively, two different size module taps 460,470. Module tap 460 is used for making connections between powerconductors 410, 420 and control conductors 431-436 of the snake cableand the input pins 33, 33a, 23, 23a of 800 and 900 series modules(modules 20b and 30b, FIG. 9). Tap power conductors 461 and 462 makecontact with cable power conductors 410 and 420 respectively throughexposed areas 463. Two tap control conductors 465, 466 are also providedon the module tap. Control conductor 465 has five exposed pads whichoverlay each of the five control conductors 431-435 in the snake cable.Connection is made to only one of the five cable conductors. The secondtap control conductor 466 is used to connect to the sixth conductor 436to create power sharing arrays of adjacent converter modules (asexplained below). Exposed pads and holes 468 and 469 make contact withthe module DC voltage input pins 23, 33 and control pins 23a, 33arespectively. A tap for use in making connections between powerconductors 410, 420 and control conductors 431-436 and the input pins13, 13a of 700 series modules (module 10b, FIG. 9) is shown in FIG. 14with similar numbering. The difference between the two module taps arein the spacing of the holes which accommodate the module pins and thecurrent carrying capacity of the power conductors.

The cable system allows flexible assembly. Both the length of the cable400, and the quantity and locations of the module taps, may be adaptedto connect virtually any number of converter modules to a standardizedpattern of power and control pins on a front-end assembly PCB 70. Oncethe locations of the converter modules have been defined, the relativepositions of the power, control signal and module taps may easily bedetermined, either by manual measurement or by computer. For example, ifa set of converter modules 10b, 20b, 30b and a front-end assembly PCB 70are arranged as shown in FIG. 9, the length of the cable 400 may bedetermined by: summing (a) the distance, L1, from the first control pin74a, past the ends of the two converter modules 10b, 20b, to the pointat which the cable takes its first bend 437 (just beyond edge 73 of PCB70), (b) the distance, L2, from the bend 437 to the point at which thecable takes its second bend 438, (c) the distance, L3, which extendsjust beyond the furthest power pin 33 on module 30b, and (d) a fixedamount of additional distance L4 to provide a small amount of material(e.g., 1/4 inch) to extend beyond the connection points at the eitherend of the cable. The types of module taps to be used, and the locationsof the taps on the cable 40, are also readily determined based on thetypes of modules used and the position of each module relative to thecontrol signal and power pins 72, 74 on the front-end PCB 70.

Once the length of the cable 400 and the types and locations of themodule taps have been determined, the cable can be assembled. One way toassemble the cable is shown in FIG. 15. In the figure a reel of cable502 feeds cable into a cutting device 504. The cutting device cuts alength of cable 400 in accordance with cable length information 505delivered to it (e.g., cable length equals "X"). The cut length of cable400 is then delivered to an insulation removal system 506 in whichportions of the snake cable conductors are exposed by burning portionsof the outer insulating layers away with a laser 507. For example,polyester film disintegrates during laser ablation. Other methods may beused to remove the insulation such as chemical decomposition, sandblasting, physical abrasion, and cutting. The locations along the cable400 at which insulation is removed is determined on the basis of thekinds and locations of the power, control signal, and module taps andthe pre-defined connections between control lines 431-436 and modulecontrol pins 13a, 23a, 33a.

A cable with portions of insulation removed 401, and the relationship ofthe cable to control, power and module taps, is shown in FIG. 16. In thefigure, cable insulation has been removed at locations 634a-634c,610a-610c, 620a-620c, 643, 644 and 665a-665c. The exposed conductors ofcontrol lines 431-433 at locations 634c-634a will be connected to pads457c-457a on control signal tap 450; exposed locations 643 and 644 ofpower conductors 410 and 420 will be connected to pads 443 and 444,respectively, on power tap 440; exposed locations 610a, 610b and 610c ofpower conductor 410 will be connected to pads 463a, 463c and 463e,respectively, on module taps 470, 460a and 460b; exposed locations 620a,620b and 620c of power conductor 420 will be connected to pads 463b,463d and 463f, respectively, on module taps 470, 460a and 460b; exposedlocations 665a, 665b and 665c of control lines 433, 432 and 431,respectively, will be connected to pads 465a, 465b and 465c,respectively, on module taps 470, 460a and 460b.

After the insulation is removed, the cable is delivered to a workstation508, (FIG. 15) for connection of the taps to the cable. Informationregarding the tap type and location is provided to the tap placementwork station 508. A supply of all types of power, control and moduletaps 509 is available at the workstation 508. Prior to placement of thetaps, an adhesive may be added to the areas of the cable surrounding theexposed areas. Solder paste is added to the exposed areas of the tapthat are to connect to the cable. An adhesive may also be added to theareas on the tap surrounding the exposed pads. The tap is then solderedto the cable, resulting in the assembly shown in FIG. 17. Exposed areason the taps (e.g., exposed areas 443, 444, 457, 465, 463) are coveredwith insulating tape (not shown) to electrically insulate the exposedareas.

After the taps are connected to the cable and insulated, the cableassembly 403 is delivered to workstation 510, at which the cable isfolded along its length (at the reference dimple 405) and the front-endpower and control signal taps are folded at 90 degree angles to thecable as shown as folded cable 481 in FIG. 18. Cable specifications arealso provided to the folding station 510 to provide the locations of thebends in the cable, e.g., bends 437, 438 (FIG. 9). The resulting snakecable 480 (FIG. 9) allows for connection to a standard front-end PCB 70while maintaining the cable conductors in a flat, vertical, orientationsuitable for snaking within a very narrow channel. The cable 480 forms alow profile bus tape that may be "snaked" around and between convertermodules, thereby increasing packaging density by saving space whichwould otherwise be required for routing bundles of interconnectionwires.

Referring again to FIG. 10A, power conductors 410 and 420 carry the DCoutput of the front-end to the DC input of the DC-DC converter modules.Five control conductors, 431 through 435, connect to the MCU at thefront-end PCB 70. As discussed above in connection with FIG. 12, five ofthe control lines are used to enable and disable one or more outputs.The sixth line 436 is used to combine adjacent converter modules intoone or more power-sharing arrays (as discussed more fully below).Alternatively, one or more of the control lines could be used to carryserially transmitted data to a control assembly located within oradjacent to the DC-DC converters.

An alternative to the snake cable 480, discussed above, employs a narrowmultilayer circuit assembly to carry power and control signals betweenthe front-end assembly and the converter modules. One such assembly,comprising a mulitlayer circuit board assembly 801, and called a "snakecircuit board" is shown in FIG. 25. The snake circuit board isparticularly well suited for DC-input power supplies in which high inputcurrents dictate heavier conductors between the front-end assembly andthe converter modules. Preferably, the snake circuit board is madesufficiently narrow to fit the width of the step 850, (in FIG. 28A). Byplacing the snake circuit board in the stepped region 850, the snakecircuit board does not add to the overall height dimension of theconverters. The input terminals of the converter modules pass throughholes in the snake circuit board 801 to make contact with theirrespective conductors.

Referring to FIG. 29, the snake circuit board is constructed of sixlayers. Starting from the top the layers are: top thin conductive layer820, insulating layer 821, heavy conductive layer 822, insulating layer823, heavy conductive layer 824, and bottom insulating layer 825.Conductive layers 822 and 824 may be, for example, constructed of 0.016inch thick copper to provide the high current carrying capacity requiredof the power conductors. The positive and negative outputs of thefront-end are connected to conductors 824 and 822, respectively, tocarry the power to the inputs of the DC-DC converter modules. Theinsulating layers may be fabricated from typical printed circuit boardmaterials. For example, layers 821 and 825 may be 0.015 inch thick FR4insulating material. Similarly, layer 823 may be 0.032 inch thick FR4material. The top conductive layer 820 which only carries low currentsignals may be made from 0.0012 inch thick copper.

Referring to FIG. 26, the arrangement of the signal conductors in thetop conductive layer 820 of snake circuit board 801 will be described.Three (vs. five in the snake cable example above) control conductors,805, 807, and 808 are connected to the MCU on the front-end PCB 70 andrun the length of the snake circuit board 801. As discussed above, thesecontrol lines are used to enable and disable one or more outputs. Eachconverter module may be connected to any one of the three controlconductors as determined by its power-up/down sequencing.

In FIG. 26, the snake circuit board 801 is configured to have convertermodules 30b, 20b, 10b (FIG. 25) connected to conductors 808, 807, 805respectively. Hole 802b is shown connected directly to the thirdconductor 808 by conductive run 812. A portion 806 of the top conductorlayer 820 is reserved for use in forming "jumper landing areas" toprovide access to either the first or second control conductors. Twojumper landing areas 810, 811 are shown formed from this reservedportion 806 of the top layer. Jumper landings 810 and 811 are shownconnected respectively to second conductor 807 and first conductor 805.Another portion of the top conductive layer 820, adjacent to the holesfor the PC terminals (b) of the converter modules, is also reserved forproviding jumper landings. Jumper landings 827 and 828 are shown in FIG.26 connected respectively to holes 804b and 803b. Conductive (e.g. lowvalue resistor) jumpers 814 and 815 are shown installed in FIG. 27. Thejumpers 814 and 815 may be soldered to the jumper landings. Asillustrated, jumpers 814, 815 respectively connect jumper landing areas810, 811 to jumper areas 828, 827 thus respectively providing connectionbetween terminals 803b, 804b and control conductors 807, 805.

Alternatively, jumpers may be formed by applying an insulating materialover the conductive layer 820 between the two jumper landings. Theinsulation may be applied for example by pad printing an epoxy andsubsequently curing the epoxy. Alternatively, solder mask material (suchas used in the manufacture of PCBs) may be used in place of the epoxy.After the insulation is applied, a conductive trace between the jumperlandings may also be applied, for example by pad printing.

A portion of the top conductive layer 820 about 0.040 inches wide, isreserved for providing a fourth conductor 809 to connect convertermodules into one or more power-sharing arrays (as discussed more fullybelow). This portion of the top layer is located at the edge of thesnake circuit board closest to the converter modules. Referring to FIGS.25 and 26, the fourth control conductor 809 is shown running along theedge of the snake circuit board. The fourth conductor may be 0.020inches wide and be separated from the remainder of the top conductivelayer using a 0.020 inch channel. The fourth conductor only connectsconverters which form a power sharing array. As shown in FIG. 26, thefourth conductor 809 connects the PR pins (c) of modules 30b and 10btogether in a power sharing array. Holes 804c and 802c which mate withthe PR converter pins (c) of converter modules 10b and 30b,respectively, are connected by conductor 809. In the event a converteris not part of an array, its PR pin is electrically isolated. Noticethat conductor 809 does not connect to the PR pin 803c of module 20b.

Referring to FIGS. 26, 28, and 33A-33C the control signal connectionsare made between the top conductive layer 820 and the control terminalsb,c of the converter modules. In order to provide adequate isolationclearance between the signal pins and the power source, clearance holes818d, 819d are made in layers 822-825 (FIG. 33C). As shown in FIG. 28,the portions 819e, 818e of holes 819, 818 in top conductive layer 820(FIG. 33A) and insulating layer 821 are made to fit the controlterminals of the converter modules, e.g. terminals 826c and 826b. Theportion 818d, 819d of the holes 819, 818 in layers 822-825 (FIG. 33C) ismade larger providing clearance between the conductive layers 822 and824 and the control terminals (FIG. 33C). Additionally, an insulatingspacer ring may be placed in holes 819, 818 to insulate the controlterminals from layers 822 and 824. The control terminals may be solderedto the top conductive layer 820. Alternatively, electrical connectingsockets may be installed in holes 818 and 819 to provide a solderlessconnection.

Referring to FIGS. 28, 30, and 33A-33C the power connection between thepositive power supply layer 824 and the positive input terminal 826awill be described. A connection hole 816 includes a conductive eyelet816b and insulating sleeve 816c. Referring to FIGS. 34A and 34B, thehole is made by first drilling a pilot hole of approximately one halfthe finished hole diameter. Then as shown in FIGS. 34A and 34B, anotherbit, for example a milling bit 900, is used to route around the hole tofinish the hole 816e (FIG. 33A). The routing is performed to remove theconductive material without having any fragments forming shorts betweenthe layers. The hole at 816d is routed to a larger diameter in layers820-822 (FIG. 33B) to provide for clearance for the insulating sleeve816c (FIG. 30) and at 816a in layer 825 (FIG. 33C) to countersink theeyelet 816b (FIG. 30). After the eyelet and insulator are inserted intothe hole, the eyelet 816b is clinched over to secure it and theinsulator 816c in the hole. The eyelet may be solder plated so that asolder joint is formed between the eyelet and the conductive layer 824when the converter terminal pin is later soldered to the eyelet. Asillustrated by the completed hole assembly of FIG. 30, the eyelet makeselectrical contact with conductive layer 824 and is insulated fromconductive layers 820 and 822.

Referring to FIG. 29 and FIGS. 33A-33C, the hole 817 for making contactto the negative power supply layer 822 is shown enlarged. The processfor forming hole 817 is virtually the same as for hole 816 describedabove. However, the larger diameter portions 817a and 817d of the holeare made respectively in layers 820-821 and 824-825 (FIGS. 33B, 33C) andthe insulating sleeve 817c is placed in the bottom portion 817d of thehole (FIG. 29). Insulating layers 821 and 825 and conductive layers 822and 824 may be made of the same thickness to allow a standard sizeeyelet and insulating spacer to be used for both holes 816 and 817.

The snake circuit boards may be fabricated completely from PCB stockusing automated machining equipment. The desired snake circuit boardshape and size is cut from the stock and the conductive traces areformed in the top conductive layer 820 by cutting channels through thetop conductive layer. For example a 0.020 diameter milling bit may beused to separate the traces. Channel 813 separates the fourth conductor809 from the remainder of the top conductive layer 820 as shown in FIG.26. Any necessary connection holes may also be machined for example, byrouting holes from the top side and then the bottom side. In this waycustom snake circuit boards may be fabricated on a lot-of-one basis in avery short time. For volume production, the snake circuit board may befabricated using customary printed circuit board processing techniques.

The snake circuit board may be connected to the front-end board usingjumper wires or taps similar to those described for use with the snakecable. As shown in FIG. 31, turns 843A-J in the snake circuit boardallow the snake circuit board to make point-to-point wiring going aroundand between converter modules while being cut from a single piece of PCBstock. Alternatively, several straight snake circuit board sections maybe interconnected using flexible taps or jumper wires.

Alternatively, a hybrid of the snake cable and the snake circuit boardmay be used to provide, for example, the current carrying capacity ofthe snake circuit board and a greater number of control lines. Oneexample of a hybrid 830 shown in FIGS. 32A-32C omits the top controlsignal layer 820 of the snake circuit board and omits the powerconductors 410 and 420 of the snake cable. In this example, power fromthe front-end is distributed by the snake circuit board 833 and the PC(power-up/down sequencing) and PR (power sharing array) control signalsare carried by the snake cable 832.

Referring to FIG. 32, the snake cable 832 has six control conductors 838as described above in connection with the snake cable 400 of FIG. 10A.The signal connections may be made to the snake using an L-shaped staple831 shown in FIG. 32A. Staple 831 serves the dual purposes of providingelectrical connection to the snake cable and also mechanical support forholding the cable in position as shown in FIG. 32A and 32B. Theelectrical connections are made using one of six pairs of flanges 835 toselectively connect to a respective one of the six conductors 838 in thecable 832. As shown in FIG. 32A, flanges 834, corresponding to thefourth control conductor, are bent toward the cable to form a staplewhich pierces the insulation and makes contact with the respectiveconductor. Electrical connection with the control terminal 836 of theconverter module is established with a contoured contact 837 as shown inFIGS. 32A and 32B. The pin 836 and contact 837 pass through a hole 841in the PCB 833 which may form a pressure fitting. The contact may alsobe soldered to the pin after the cable and PCB are assembled.Alternatively the contoured contact may be formed into a cylindricalsleeve to encircle the pin 836 providing additional mechanical stabilityto the staple 831 and better electrical contact. Hole 841 is made tohave a large diameter in the top four layers (two insulation and twopower conductor layers) of the snake circuit board to prevent shortswith the power conductors. The hole has a smaller diameter in the bottominsulation layer to provide mechanical stability to the PCB. Aninsulating spacer, such as described above, may be placed over the pinand contact to provide additional protection against shorts with thepower conductors 839 and 840 in the snake circuit board and additionalmechanical support to the snake hybrid assembly. Hole 841 may be made ofa uniform diameter to snugly fit the insulating spacer. The staple 831may be provided with additional flanges for mechanically securing thecable to the staple. For example flange 842 may be provided at thebottom of the staple 831 as shown in FIG. 32B. The additional flangesare arranged to avoid making contact with any of the other conductors inthe cable. Staple 831 may be provided with an insulating coating overall areas except those that are required to make electrical contact. Thesixth conductor is used to connect adjacent converters into powersharing arrays (as explained below). As an alternative, a tap similar tomodule taps 460, 470 described above, may be modified (omitting toppower conductors 461, 462) to provide the signal connections. The powerconnections to power conductors 839 and 840 are made in the same way asdescribed above for the snake circuit board.

Alternatively, one or more printed circuit boards may be used to providethe interconnection among the components in the same fashion that thefront-end PCB provides the interconnect for the front-end components, orthe interconnection may be achieved using a point-to-point wire cableharness between the front-end and each DC-DC converter.

FIG. 5 shows a system block diagram of a computer aided design system100 for configuring power supplies of the kind shown in FIGS. 2 and 9.The system 100 enables users to define and enter functional requirementssuch as voltage input, voltage outputs, output power levels, thermalenvironment, and certification requirements for the power system;establish a complement of modular power components such as DC-DCconverter modules and front-end components to realize the power system;and define the configuration, shape, and size of the mechanical packagefor the power system, including the mounting arrangement of the powercomponents on one or more metal mounting plates, as a means of meetingapplication-specific performance and configuration requirements. Theoutputs of the design system 100 include mechanical informationnecessary to machine, or otherwise fabricate, the metal substrate aswell as information necessary to create means for connecting the inputsource to the module input pins and for making connections to converteroutput pins and other primary and secondary control pins.

The system 100 is used by designers who wish to specify and acquire ahigh-density power supply which is customized to their uniqueperformance requirements. The user interface 110, which runs on adesktop computer (e.g., a personal computer or a workstation), isintended to be used by design engineers at OEM or customer locations.Referring to FIG. 5, a user interface 110, including a mouse 116, akeyboard 114, and a visual display device 112, such as a color CRTmonitor, allows the user to interact with system 100. The system 100provides a menu bar driven interface for accessing a series of screendisplays each of which prompts the user to enter the requisiteinformation.

Familiarity with menu driven computer interfaces is assumed. Generally,a cursor (e.g., cursor 246 in FIG. 7A) on the screen is moved using themouse 116 or other pointing device. An option highlighted or pointed toby the cursor may be selected for example, by double clicking on theleft mouse button. Data may be entered by moving the cursor to theappropriate location or field on the screen display and then typing theinformation using the keyboard 114 into the field. In some cases such asa multiple output power system, several items (outputs) may bespecified. The user may complete a data entry form for an item and addthe completed item to a list using the enter key or other appropriateaction. In this way, the system may collect the specifications for eachitem.

An interface to a remote computer 190 which provides remote converterdesign services such as DC-DC converter design generation 192, pricinginformation 193, delivery information 194, and user registration andsoftware and specification updates 195 is shown in FIG. 5. The remotecomputer 190 may be located for example at a power supply manufacturer'sfacility.

Database 180 stores design configuration specifications generated by thesystem 100. Three additional databases 120, a selection criteriadatabase 122, a rules database 124, and a standard componentspecifications database 126, may provide information to the system asdescribed more fully below. Five general processes, the system inputspecification process 130, the module output specification process 140,the thermal analysis and design process 150, the mechanical layoutsystem 160, and the options specification process 170 are depicted inFIG. 5. Each is a step in the power supply design process and will bedescribed in connection with FIGS. 7A-7H which are representations ofthe display screens presented to the user on visual display 112 duringthe data entry process.

The system 100 presents the user with a menu bar 225 as shown in FIG.7A. The menu bar 225 provides means for accessing a series of data entryforms on the screen display each of which prompts the user to entercertain power system specifications. Specifications entered by the userare stored in the design configuration database 180. Examples of dataentry screens which may be presented to the user by selection of therespective "Input Specs," "Output Specs," "Thermal," "Mechanical,""Options," and "Project Info" icons on the specification menu bar 225are shown in FIGS. 7B through 7H. Each screen prompts the user to enterspecifications (discussed more fully below) for the power system 40being designed which are then collected and stored by the power supplyspecification system in the design configuration database 180. The menubar 225 is always available to allow the user to move between screens,however, certain menu options may be shaded differently to indicate theyare not available. An information area 226 shown in FIG. 7 may be usedby system 100 to provide messages to the user.

The design process using the system 100 will be described with referenceto FIG. 8 which is a basic flow chart of the system 100 operation andwith reference to FIGS. 7A-7H.

User Registration/Software Updates

Referring to process block 281 in FIG. 8, the system 100 will connect toa remote computer 190 (FIG. 5) via a modem or other interface at thebeginning of each design session. Upon connecting theregistration/updates system 195 is accessed to notify the user if it isnecessary to update the software or database using information that hasbecome available since the last installation or update of the userinterface 110.

Input Specifications

As shown by block 282 in FIG. 8, the power supply design process beginswith the user defining the input specifications. The system inputspecifications 130 (FIG. 5) are collected from the user with a dataentry screen as shown in FIG. 7B. The user specifies the input voltagerange 202, the frequency of the AC input voltage 203 if applicable, andthe EMI filter requirements 206 (e.g. FCC class A). The user mayadditionally provide the surge 207 and fast transient 208 inputrequirements and the ride-through 209 and power-fail timing 210specifications. A power-factor correcting ("PFC") front-end, anauto-ranging rectifier-capacitor input front-end, or a DC inputfront-end may be selected using field 201. In FIG. 7B, the auto-rangingfront-end option is shown selected as indicated by the darkenedselection circle 204 in field 201. The system 100 may automaticallyprovide pre-defined default specifications for the user to accept as isor with changes. For example, the system may provide a default inputvoltage range where only a nominal voltage is entered. A list ofavailable options in entry fields may also be provided such as indicatedby the list pull-down arrow 205 in the Input EMI field 206.

The ride-through time (field 209) may be defined as the minimumuninterrupted length of time after the input voltage is removed that thepower supply outputs will continue to operate from energy stored in thefront-end storage capacitors. The Power Fail entry (field 210) specifiesthe minimum amount of time after a power fail signal is provided thatthe power supply outputs will continue to operate within specifications.This information is used by the system 100 to select appropriatecapacitors for the HUB 92 (FIGS. 2A, 2B).

Output Specification

Referring to FIG. 8, the output specifications are collected by thesystem as shown by block 283 after the input specifications have beendefined. The module output specifications 140 (FIG. 5) are collectedusing an output specifications screen such as shown in FIG. 7C. For eachoutput, the user specifies the DC output voltage 211, the power levelsfor the output, both average 213 and surge 214, and the over-voltage 212and current-limit 215 set points as shown in FIG. 7C.

The average power rating (field 213) may be used to define the averagepower level that the converter must be capable of delivering for periodsof time which are long compared to the thermal time constant of thepower system. Conversely, the surge power rating (field 214) may be usedto define the peak power level that the converter must be capable ofdelivering for durations of time which are short relative to the thermaltime constant of the power system. For example, the average powerrequired by a disk drive system load may be 100 Watts, whereas 250 Wattsmay be required by the disk drive system during the short periods oftime that the drive motors are being started up. The average and surgevalues of output current may be specified as shown in fields 213 and 214of FIG. 7C as an alternative to specifying the power values.

The power system 40 being designed may be required to supply severaloutputs. Therefore, the user may add another output specification,update or delete a previously entered output specification, or requestanother blank output specification form using the three action buttons227. As shown, each output is assigned a numbered tab 224 which the usermay select with the cursor to review the specifications for therespective output.

The user may also specify the timing and sequencing for each outputduring power-up, power-down, and power-fail conditions as shown in FIG.7C. The timing and sequencing information is used to program the MCU.The number fields 218, 220, 222 specify the queue position of the outputand the time fields 219, 221, 223 specify the delay.

The system automatically enforces rules which may limit the designoptions available to the user to aid in ensuring the feasibility of thedesign. As discussed further below, the rules may be based on manyfactors, including limitations imposed by the selected manufacturingmaterials, processes, and equipment. One example of such a rule relatesto the maximum number of control lines available in the wiring systemselected to build the power supply 40. The number of control linesavailable in the wiring system may limit the number of stages in thepower-up, power-down, and brown-out control sequences. For example, thesnake cable system 480 described above has five separate control linessupporting up to five steps in the sequence as compared to three stepsfor the snake circuit board 801, and eight or more steps in the hybridsnake system. A full printed circuit board or a serial communicationoption may allow for even more (or an unlimited number of) steps in thesequence.

Field 216 allows the user to choose whether an output connector, such asModuMate™ connector 90 in FIG. 2A, will be provided to connect to themodule output pins. The user may also optionally specify the module sizeusing field 216. The system 100 will then determine how many modules ofthe specified size are needed to meet the output specification. Themaximum baseplate temperature 217 may also be specified. The user leavesthe output specification screen after all of the outputs have beenspecified.

Converter Module Design

Referring to block 284 in FIG. 8, the converter modules are designedafter the input and output specifications have been collected. Thesystem 100 may connect to the remote computer 190, for example by modem,to generate the designs for the DC-DC converter modules necessary tomeet the user-defined input and output specifications. The input andoutput specifications stored in the design configuration database 180shown in FIG. 5 are sent to the DC-DC converter design generationprocess 192 (FIG. 5) which designs the complement of converters requiredto build the power system 40, as defined by the user and returns thespecifications for the converter modules. For example, specificationsreturned by the design generation process 192 may include the DC-DCconverter package size, conversion efficiency, and module part numbers.The system 100 may connect to the remote computer 190 after all of theoutputs are specified in step 283 to obtain all of the converter moduledesigns and specifications in a single step. Alternatively, an iterativeprocedure may be used in which the remote computer is contacted and thespecifications obtained for the DC-DC converter(s) for each output aftereach output is specified in step 283.

Unless the user has chosen to specify DC-DC converter package sizes, theremote converter designer 192 seeks to minimize the volume occupied bythe converter modules and thus selects a complement of package sizesrequired to implement the power system 40 in the least amount of volume.For example, if the user requires that 12 Volts be delivered at 175Watts, the selection software and rules database will specify an 800Series package 20, since this is the smallest package which can providethis amount of power. Where the power required for one output voltageexceeds that which can be delivered from a single module, the remoteconverter designer 192 will specify the requisite number of modulepackages which will satisfy the output requirements when operated in apower sharing array. For example, the remote DC-DC converter designgenerator 192 will specify an array of two 900 Series packages, eachcapable of delivering up to 600 Watts, to satisfy a 48 Volt 850 Wattoutput requirement. On the other hand, if only 700 watts is requiredfrom the 48 Volt output, then the DC-DC converter design generator 192would specify an array of three 800 Series packages which can deliverthe power (250 Watts per module) in less volume than two, larger, 900Series packages.

After each output's package size, power and efficiency ratings aredetermined by the remote converter designer 192, this data is returnedto the system 100 and stored in the design configuration database 180. Asystem 192 for automatically generating DC-DC converter designs whichare optimized with respect to selected criteria such as efficiency orcost is described in commonly assigned U.S. patent application Ser. No.08/631,890, Montminy, et al, entitled "Configuring Power Converters" andincorporated here by reference.

As an alternative to the remote computer 190 generating custom converterdesigns for each system, a standard component database 126 as shown inFIG. 5 may be provided with specifications of pre-configured DC-DCconverter models. The system 100 may then determine whether any"standard" DC-DC converter models are available to satisfy eachparticular output requirement. The term "standard" is used to refer toconverter modules which have been previously designed, for example, tosatisfy commonly required output voltages and power levels. For example,a 48 Volt 600 Watt or a 5 Volt 400 watt converter may be available as"pre-configured" models in 900 Series packages 30. If pre-configuredunits are available, the model numbers and the required quantity ofunits would then be stored in the design configuration database 180. Thesystem 100 may be set up to use only custom converter designs, onlystandard designs, or a mix using custom designs only when pre-configureddesigns are not suitable.

Front-End/HUB Selection

Referring to block 285 of FIG. 8, the front-end circuitry is selectedafter the complement of DC-DC converter modules required to meet theoutput requirements are specified. The system 100 uses the modulespecifications generated by the output converter design generator 192,including the output power and efficiency, and the front-end and EMIspecifications from the input specifications system 130 stored in thedesign configuration database to select the balance of the powercomponents needed to implement the power system 40, i.e., the front-endand the HUB 92. The components suitable for the design are chosen from aselection of pre-configured options stored in the standard componentsdatabase 126.

In selecting the front-end assembly, the system 100 calculates themaximum power which the front-end assembly must deliver using thespecifications of the complement of DC-DC converter modules. The systemselects the physically smallest front-end circuit assemblies of the typedefined by the user in the input specification section.

Referring to FIG. 5, the system 100 may select from a range of availablefront-end options stored in the standard components database 126. Thedatabase 126 might include for example, four differentpower-factor-corrected front-end assemblies, as shown in FIGS. 20Athrough 20D, capable of delivering maximum power levels of 400 (FIGS.20A and 20B) and 800 (FIGS. 20C and 20D) Watts. The database may alsoinclude four different auto-ranging front-end assemblies, as shown inFIGS. 22A through 22D, capable of delivering maximum power levels of 500(FIGS. 22A and 22B) and 1000 (FIGS. 22C and 22D) Watts.

In general there are at least two mechanical configurations for eachfront-end circuit assembly available. The user can choose betweendifferent mechanical designs of the same front-end circuit to suit hispackaging requirements. For example, FIGS. 22A and 22B show twodifferent mechanical layouts for the same 500 Watt auto-rangingfront-end circuitry. All front-end options suitable for the design arestored in the design configuration database 180 and are available to theuser for selection.

The system 100 also chooses the physically smallest HUB 92 (FIG. 2A)which is compatible with the specified front-end type and which can meetthe requirement specified by the user. The selection of HUBspecifications are stored in the standard components database 126 whichmight include, for example, four different capacitor assemblies for usewith power-factor-corrected front-ends, as shown in FIGS. 21E through21H, and four different capacitor assemblies for use with auto-rangingfront-ends, as shown in FIGS. 21A through 21D.

Alternatively, a custom front-end design service may be provided by theremote computer system 190 in the same manner as with the custom outputconverter design generator 192 discussed above.

Mechanical

Referring to block 286 in FIG. 8, the user may proceed to the mechanicalspecification screen after the complement of power components i.e., theconverter modules and the front-end, have been designed or selected andthe mechanical characteristics of the power components are stored in thedesign configuration database 180. The mechanical layout system 160(FIG. 5) is used to design the physical layout, including the locationand orientation of the various power components within the power system40.

Referring to FIG. 7D, the user is presented with an outline of each ofthe power components generated by the system 100 using the remotecomputer 190, including the DC-DC converter modules and the front-end.In FIG. 7D, icons 231, 232, 233, and 234, comprising the outlines of theDC-DC converter modules 10b, 20b, 30b, and the selected front-endassembly respectively, are arranged at the top of the screen. An iconfor each of the power components in the complement of components isprovided. Since the HUB 92 is mounted separately from the power supplyassembly 40, it is not represented on the mechanical layout screen.

Since more than one mechanical configuration for the front-end assemblymay be available, the system 100 may allow the user to switch back andforth between the various front-end options available for the design tofacilitate optimization of the mechanical design. For example, thesystem may allow the user to scroll through the available front-endoptions by clicking on the front-end icon 234. Alternatively, icons foreach of the front-end options may be displayed simultaneously with theun-selected options shown as shaded outlines. The user may then switchbetween the options by selecting the desired configuration.

The user may draw an outline of the desired mounting plate 80 usingdrawing tools 228 and then position the power components on the mountingsurface as desired by dragging the icons to the corresponding locations.Referring to FIG. 7D, a layout area 230 corresponding to the desiredmounting plate 80 is shown drawn. The layout area 230 is a virtualsurface upon which the icons 231, 232, 233, 234 representing theconverter modules 10b, 20b, and 30b and the selected front-end assemblymay be arranged. Referring to FIG. 7E, a partially arranged mechanicallayout is shown. Converter modules 10b and 20b (icons 231 and 232) havebeen positioned on the layout area 230 and module 30b (233) is in theprocess of being dragged to the layout area 230. By using the mouse 116to move the icons, the user may place the components at any location inthe layout area of the screen, thereby defining the component positionsin the completed power system 40. The user may also specify varioustypes of holes and threading in the mounting plate 80 to facilitatemounting of the power supply inside the user's equipment usingadditional drawing tools (not shown).

The user may specify maximum dimensions for one or more of the outsidedimensions of the power supply 40. The user may directly adjust thedimensions of the peripheral edges of the mounting surface (providedthat the edges remain outside of the region in which the converters areplaced) by dragging the lines with the mouse. Alternatively, the usercan adjust the dimensions directly by selecting an edge of the area 230with the mouse and entering dimensional data directly in field 236 viathe keyboard 114. Dimension units are selected using field 235. In field229, the user may select the mounting plate thickness, e.g., 0.187",0.25", 0.32", or 0.5" depending on his mechanical and thermalrequirements.

Alternatively, the user may simply position the power components in thedesired positions on the screen and draw the outline 237 of the mountingsurface by moving the cursor 246 as shown by the dotted line in FIG. 7F.Alternatively, the user may elect to have the system 100 draw theoutline of the mounting surface automatically. The user may choose tohave the system draw either a rectangular mounting surface or anirregularly shaped (such as 230 in FIG. 7D) mounting surface to conformto the perimeter of the arranged power components.

The mechanical layout system 160 may alternatively be operated in a"rubber band" periphery mode in which the designer is presented with adisplay of all of the modules pre-arranged on a mounting surface. A verysimple pre-arrangement strategy may be used. For example, DC-DCconverters may be lined up side-by-side with their outputs facing oneperipheral edge of the mounting surface and front-end components may belined up side-by-side with their inputs facing a parallel peripheraledge of the surface. The initial mounting surface may default todimensions just large enough to accommodate the complement of convertersand front-end components, subject to positional design rules (e.g., asdescribed below) and cooling requirements. The user may then repositionthe modules, power sharing arrays, or front-end components. As thecomponents are moved about, the peripheral edge of the mounting platewill automatically expand or contract like a "rubber band" to align withconverter outputs and front-end inputs. Real-time thermal calculationsmay be performed to ensure that the X, Y and Z dimensions are neversmaller than those required to cool the system. The other featuresdescribed above for the mechanical layout system may also be provided inthe rubber band periphery mode.

The mechanical layout system 160 automatically enforces a set of rulesstored in the rules database 124 which limit the mechanical layout beingcreated by the user. The rules may be based upon factors which include,but are not limited to, manufacturing process, material, equipmentlimitations, safety specifications and agency approval specifications,environmental considerations such as temperature and airflow imposed bythe thermal analysis and design system 150, and user specified size andshape constraints stored in the design configuration database 180.

Using the rules, the mechanical layout system 160 restricts theplacement and orientation of the components and also the size and shapeof the power system. In other words, as the user positions andrepositions the power component icons and sets the size of the mountingsurface, the mechanical layout system will enforce the rules eitherallowing or not allowing the action attempted by the user. Preferably, aprohibited action is accompanied by a message alerting the user to theproblem with, and the rule which prohibits, the attempted action.Several examples of rules which may be imposed by the mechanical layoutsystem are discussed below.

Maximum Size Rule

The maximum allowable size of the mounting plate 80 may be limited bythe downstream processes (described below) used in their manufacture.For example, the choice of machining equipment might limit the maximummounting plate dimensions to 12 inches by 18 inches. Such amanufacturing system limitation may be enforced by the mechanical layoutsystem. The layout area 230 initially may be set to a default size whichcorresponds to the maximum mounting plate dimensions. The user can thenadjust it to the desired size. Alternatively, the size may be set by theuser with the system preventing expansion of the size to beyondmanufacturable dimensions. For power system designs requiring more thanthe area provide by the maximum mounting plate size, multiple stackedassemblies may be designed for assembly into a single power system 40.An example of a multiple mounting plate power system is shownschematically in FIG. 19. The system may also enforce rules based uponthe user defined specifications such as maximum mounting plate sizelimitations.

Another manufacturing system imposed limitation that may arise insystems capable of machining mounting plate stock into a mounting platewith integral heat sink fins (described further below) is the maximumheight of the heat sink fins. In such a system, the mechanical layoutsystem 160 may also enforce a maximum heatsink-fin height limitationsuch as, for example, 1 inch.

The mechanical layout system 160 will attempt to work within the userspecified constraints to arrive at a design solution which providessufficient surface area to mount all of the required assemblies andprovide for adequate system cooling. If the dimensional constraints areinconsistent with either requirement, the user will be notified to makeadjustments. In an alternate system embodiment, the system may offer tofind an alternate solutions for the user. If the user redefines themaximum temperature for the system baseplate, the remote converterdesigner 192 may be re-called to redesign the DC-DC converter modules.

Module Grouping Rule

If two or more modules are used together to form a power sharing arrayfor one output, the mechanical layout system may require that they beplaced logically adjacent to each other. In other words, no module whichis not part of an array may be located in between two modules which forma part of the array. This limitation is a manufacturing limitationimposed for the convenience of the preferred snake cable systemdiscussed above in connection with FIGS. 9-18. Forcing modules in apower sharing array to be adjacent to each other allows a single, thesixth, control signal conductor 436 of snake cable 400 (or fourthconductor 809 of snake circuit board 801) to be used for connecting allof the modules within each of the arrays. The conductor may be cut atthe power sharing array boundaries thereby isolating the conductor fromthe other modules or arrays.

An alternative method for enforcing the array adjacency requirement inthe mechanical layout system and making the layout task simpler is tocreate a single icon for the entire array. The array icon represents theoutlines of all of the modules in the array but is positioned by theuser as a single graphical object.

Input/Output Positioning Rule

The mechanical layout system 160 may require that all DC-DC converteroutputs face a peripheral edge 81a, 81b, 81c of the mounting surface sothat output connectors 90 (FIG. 2A) are externally accessible. Thisensures that there is always a minimum of two solutions for configuringthe snake cable or snake circuit board to connect to all of the modules.Minimum spacings are also enforced between converter output pins andother live parts such as the input connector 60 pins and the outputconnections (e.g. 25, 26, 27 FIG. 2A) of the active front-endassemblies. Output pins of one converter module may not be placeddirectly adjacent to the input pins of another converter module.

Module Clearance Rules

Module clearance rules enforced during the mechanical layout phase ofthe design, ensure that adequate space is left between modules to routethe snake cable or snake circuit board from the front-end to each of themodules. The module clearance rules are designed to allow for themechanical mounting of the output connectors 90 also. In some designsthe thermal parameters may impose more stringent module clearance ruleswhich will be enforced by the system.

Module Orientation Rule

Generally, the modules may be aligned with either the X or Y dimension.In other words each module only may be rotated in 90 degree increments.This orientation rule also applies to converter modules forming a partof power sharing arrays so that an array is capable of "turning acorner" of the mounting plate.

PCB Limitations Rules

The PCB traces must be spaced a minimum distance apart from each otherto satisfy certain safety or regulatory agency rules such asUnderwriter's Laboratories and the Canadian Standards Association.

Manufacturability & Testability Rules

Other rules may also be incorporated and enforced by the system toensure the manufacturability and testability of the power system usingthe equipment available. For example, the internal radii of corners inthe mounting plate 80 may default to 0.125 inches for the convenience ofthe tooling used to fabricate the mounting plates.

Thermal Specifications

Referring to block 287 in FIG. 8, the thermal design 150 is performedafter the mechanical layout 160 is completed. The thermal environmentdata entry screen shown in FIG. 7G may be used to specify the thermalenvironment in which the power system 40 will be operated. The user isprompted to enter values for the maximum ambient air temperature 238,the minimum available rate of air flow 239, and the airflow direction240. The system presents the user with reduced size layout area 230 toindicate the air flow direction. The maximum heatsink fin height 241 maybe specified by the user or a calculated fin height 242 may be providedby the system as shown in FIG. 7G. Additionally, the user may berequested to provide a maximum operating temperature for the mountingplate. Optionally, the system may request an altitude specification foruse in the thermal design.

The design system 100 uses converter efficiency values anduser-specified converter output power ratings which are stored in thedesign configuration database 180 to calculate the power dissipation inthe converter modules, the front-end assembly, and the overall system40. The system 100 uses this information to evaluate system thermaloperating requirements and to select and/or design the appropriate heatsinks as discussed in detail below.

The system first evaluates the power dissipation in each module and thetotal power dissipation on each mounting plate. The average heatsinkairflow and maximum delta temperature for each module are alsodetermined by the system. Using these values an appropriate heatsink maybe selected using a look-up table of heatsink parameters for various finheights, and heatsink configurations. The heatsink-to-ambient thermalconductance for several heatsink configurations and airflow conditionsmay be determined empirically and provided in a look-up table. Anaverage conductance value for the entire heatsink may be provided.Element values for each element in a finite element model of eachheatsink (discussed more fully below) may be provided in addition to oras an alternative to the average conductance value.

Because of the wide variety of possible mounting plate sizes and shapes,and airflow direction, and component placement on the mounting plate, afinite element model of the thermal design is created and analyzed. Theheatsink is divided into a number of equal sized elements. For example,0.2×0.2 inch or 10 mm square elements may be used. Each element wouldhave a central node. Each node is assumed to be isothermal having auniform temperature. Referring to FIG. 23, a simple nine node example,nodes N1 through N9, of the finite element thermal analysis isillustrated. Each node is shown thermally connected to its adjacentnodes by thermal conductances J. For example, node N1 is connected tonodes N2 and N4 by conductances J₁₋₂ and J₁₋₄, respectively. A standardelement size may be used for evaluating each design. Using a constantelement size, the conductance between each element may be the sameconstant. For example, the thermal conductance may be 1.25 Watts/degreeC for a 6 millimeter thick mounting plate and using 10 millimeter squareelements. Optionally, a different conductance value, JF, may bespecified for the conductance between elements connected by fins sincethe fins increase the thermal conductance. Thermal losses along theedges may be ignored as shown in the example of node N1 in FIG. 23.Alternatively, a thermal conductance value for the conduction between anode and an edge may be specified. For example, J/2, may be used toaccount for edge losses.

The convection conductances, H are also specified for the heatsink. Forexample the convection conductance from the heatsink to the ambient atnode N1 is H_(1-C). The convection conductances may be defined as afunction of convective film coefficient which may vary along the lengthof the heatsink as ambient air temperature and airflow vary. Forexample, air flow from the top of the page toward the bottom in FIG. 23may yield conductance values of 70, 80, and 90 Watts/degree C-squaremeter for nodes N1-N3, N4-N6, N7-N9, respectively or 0.007, 0.008, and0.009 Watts/degree C for 10 millimeter square elements, respectively.Values for the convection conductance may be stored in a look-up tablefor various heatsink configurations and fin heights.

The power dissipation for each module may be mapped and transferred ontothe respectively aligned nodes. For this purpose, a finite element powerdissipation model of each module may be provided based upon thecomponent locations within the module. Alternatively, an isothermalpower dissipation model in which the power dissipation of the module isevenly distributed to each of the nodes aligned with the module. Ineither case, the heat generated by each module is mapped onto therespectively aligned nodes using the module locations defined during themechanical layout design. In FIG. 23, power dissipation values P1through P9 are shown mapped onto nodes N1 through N9.

A series of simultaneous heatflow equations, one equation for each node,is written. For example, the heatflow equation (EQN 1) for node N1 maybe written (using a sign convention where heat flowing into the node ispositive) as:

    J.sub.1-2 (T.sub.2 -T.sub.1)+J.sub.1-4 (T.sub.4 -T.sub.1)+H.sub.1-C (T.sub.1 -T.sub.C)+1 watt=0                               EQN 1

where T₁, T₂, T₄, and T_(C) are the temperatures of nodes 1, 2, 4 andthe ambient air, and 1 watt is the power dissipated into node 1.

The series of simultaneous equations are then solved producing a thermalmap of the node temperatures. A comparison of each node temperature withthe specified maximum mounting plate temperature may be performed by thesystem. If any node temperature exceeds the maximum mounting platetemperature, then the heatsink design may be updated and a satisfactoryheatsink design reached in an iterative manner. A visual map of thetemperatures, for example a color thermal topography of the mountingplate, may be displayed for review by the user.

It will be appreciated that any number of heatsink design methodologiesmay be implemented. For example, the system may use the total powerdissipation, ambient air temperature, and maximum mounting platetemperature to estimate the heatsink requirements and select a heatsinkfor the beginning of an iterative thermal design. The selection may thenbe analyzed using the finite element model and changed if necessary.

A finite element model may be set up for a maximum sized mounting plate.For example, a 12×18 inch mounting plate using 0.2 inch square elementswould yield a 5400 node generalized model. The actual mounting plate maythen be mapped onto the generalized model setting the conductances,power input, and temperatures for all unmapped nodes to zero. In thisway, a single model with one generalized set of simultaneous equationsmay be used to evaluate every possible heatsink design.

As described above, the user may enter maximum values for any of the X,Y, or Z dimensions respectively corresponding to the width, length, andheight of the power supply 40. The height dimension may limit the heightof the heatsink fins available for the power system 40 and thus limitthe heatsink options available for the design. Three heatsink optionsmay be provided to satisfy the thermal requirements: 1) a mounting platewith the integral full surface heatsink as shown in FIGS. 3A, 3B, 2) themounting plate with individual heat sinks as shown in FIG. 4, or 3) abare mounting plate as shown in FIG. 2A. Height limitations may alsoaffect the component density (module spacing) on the mounting plate. Forexample, as the height limit is reduced, the surface area requirementsto provide adequate cooling may increase. Whenever the user specifies anX, Y, or Z dimension, the system may default to a value which is thegreater of the value specified by the user or the minimum valuecalculated by the system as necessary to provide adequate cooling.

Optionally, an on-screen display may be provided to show the X, Y and Zdimensions, and total system volume, V, of the power system 40 in realtime. A real time side view of the heat sink showing fin density andrelative fin height may optionally be provided. Alternatively, the realtime computations may be suspended to facilitate faster system response.In such a system the user may request recalculation of the volume or finheight at any time.

Options

Referring to block 288 in FIG. 8, the user proceeds to the optionsspecification 170 (FIG. 5) after the thermal design is completed. Asample options specification screen is shown in FIG. 7H. The user maydesignate the safety agency certification requirements 243, theprocessing requirements (commercial, industrial, or military) 244, andcabling requirements 245 for the power system 40. The system 100 storesthis information in the design configuration database.

Project Information

Referring to block 289 in FIG. 8, the user proceeds to the projectinformation screen which collects information about the designincluding, for example, the designer's name and company information,after the design has been completed. After the project information iscollected the system 100 again connects to the remote computer 190transmitting the design information from the design configurationdatabase 180 to the pricing and delivery systems 193 and 194. Thepricing and delivery systems then evaluate the design and return priceand delivery quotes to the user and a part number which will enable theuser to order the complete power system.

Referring to block 290 in FIG. 8, the user may order the power system 40using the part number provided by the remote computer 190. The user mayplace the order using an order placement system which may be provided aspart of the project information screen. An ordering menu option may beprovided on system 100 to collect the ordering information, includingquantity at the quoted price and delivery time and payment details. Thesystem 100 may then transmit the ordering information to the remotefacility 190 for final confirmation of the price and delivery terms.Alternatively, the user may call an order placement telephone number tospeak with a sales person who may manually take the required informationand confirm the price and delivery details. An automated telephoneordering system may also be provided.

Referring to FIGS. 5 and 6, the order entry and manufacturing system 300will be described. Once a purchase order is actually received, thedelivery and price are confirmed again since the circumstances may havechanged between the initial quote by remote computer 190 in the projectinformation step and the actual order placement. A pricing system 193receives the raw DC-DC converter specifications and automaticallygenerates a cost for the converter modules in the manner described incommonly assigned, copending application, Ser. No. 08/635,026, entitledConfiguring Power Converters, filed on Apr. 19, 1996, and incorporatedhere by reference. At the system level, the pricing system 193 uses theaggregate of the DC/DC converter costs previously generated incombination with details contained within the raw system specificationsto determine the total system pricing. For example, these details mayinclude cable lengths and quantities, mounting plate geometry, andfront-end unit types used and cost algorithms for each such assembly.

The delivery system 194 also receives the raw system specifications andgenerates module level delivery dates which are then used in thegeneration of a system level delivery date. The delivery system 194communicates with a computer integrated manufacturing ("CIM") system. Inparticular, a production scheduler 340 in the CIM provides supply anddemand information enabling the delivery system 194 to provide adelivery date based upon the next available production time slot.

Upon receipt of an order from ordering system 330, the productionscheduler 340 activates the system manufacturing interface ("SMI") 375.The SMI 375 receives the raw system specifications and generates all ofthe detailed manufacturing specifications for all of the componentsnecessary to build the system and also generates assembly and testspecifications and procedures for the system level assembly. Forexample, the SMI 375 generates part numbers for all of the partsincluding those manufactured by manufacturing lines 350 and 360 as wellas those that may need to be ordered from outside vendors. All detailsfor each part such as the description and quantity are also provided onthe bill of materials ("BOM"). The BOM, including all of the partdetails, for each system is stored in a database (not shown). The SMI375 also generates specifications for the (1) internal wiring of thepower system potentially including snake cable, snake circuit board,hybrid snake, or standard PCB specifications, (2) output cables, (3) HUB92 cable, (4) programmable device specifications for the MCU in the PPU,(5) all labels for the system and components in the system, (6) producttest specifications, (7) automated machining specifications from themechanical layout information to fabricate the metal mounting plate andheatsinks if necessary, (8) module specifications for the converter andfront-end modules to be manufactured on the module line 350, and (9)assembly instruction display files for workers performing manualassembly tasks.

The SMI 375 generates the requisite specifications for fabrication ofthe snake wiring i.e., the snake cable, snake circuit board, or hybrid,assembly. The module placement clearance and orientation rules ensurethat a viable snake solution may be found. For example, the clearanceand placement rules enforced during the mechanical layout sessionguarantee that there will be enough space to snake the snake wiringsystem between the components. They also ensure that there will beenough space for the requisite number of conductors on the snake circuitboard. Since the module orientation rules ensure that the DC-DCconverter module outputs directly face the peripheral edges of themounting plate, all module inputs will face the interior of the PPUmounting plate. Thus, all module inputs may be connected by routing thesnake wiring system in a clockwise or counter-clockwise direction fromthe front-end location at any point on the mounting plate. This ensuresthat there are at least two snake wiring solutions for each design.Additional solutions may be found by locating the front-end at a midpoint along the snake with converter modules connected on clock-wiseextending and on counter-clockwise extending ends. Since all of themodules in a power-sharing array must be adjacently located, there willalways be a solution in which the sixth conductor of the snake cable isavailable to connect all of the converters in the power-sharing array.

An additional snake circuit board solution (called the maximum widthsnake circuit board) may be used to reduce power losses by expanding thesnake circuit board to fill all of the available space. Of course, thesnake circuit board may not extend beyond the boundaries of the mountingplate or cover any keepout areas, such as the PPU mounting holes definedby the user. A minimum width snake circuit board solution is shown inFIG. 35A for contrast with the maximum width snake circuit boardsolution for the same layout shown in FIG. 35B. The outline of themaximum width snake circuit board is generated by forming a closed loopin either a clock-wise or counter-clockwise direction starting from theconnection points on the front-end through each of the power convertersin sequence and returning back to the starting point on the front-end.The top layer signal interconnections are developed in the same manneras for the minimum width snake circuit board and may be identical tothose of the minimum width solution.

The SMI chooses the optimal design solution for the snake based upon themechanical layout of the power components. This is particularlyimportant for low voltage DC input (e.g., 5-24 VDC) designs because ofthe higher input currents. First each feasible snake routing possibilityis determined. Then the power loss is calculated for each routing usingthe length of the snake between each module and the front-end and theinput current for the respective module. The route with the lowest powerloss is chosen as the optimal design solution for the snake. The designdetails (including the route, overall length, bends, taps, andintermediate dimensions) for the optimal snake are provided to thescheduler 340 for manufacture of the snake cable, snake circuit board,or snake hybrid and assembly of the snake onto the PPU.

The SMI 375 provides the specifications to the production scheduler 340which orchestrates the production and ordering of all of the componentsnecessary to build the system. It checks the stock status of all parts,schedules the manufacture of converters or other fabricated modules, andorders externally purchased or manufactured parts, if required. Theproduction scheduler 340 plans the component manufacturing for themodules on the module line 350 and the other, system level, componentson the system line 360.

The scheduler 340 may be electronically linked to automated machiningcenters 361 (FIG. 6) on the system line 360 which may fabricate themetal substrate and heatsinks. The production scheduler 340 transfersthe automated machining information to the appropriate automatedmachining center which will fabricate the metal mounting plate. Ifnecessary, the completed plate may be sent to an outside vendor forchemical treatment or alternatively, to an automatic treatment stationon the system line 360.

The scheduler may also be connected to manual or automatic cablefabrication equipment which may fabricate the requisite cableassemblies. The scheduler 340 transfers the cable specifications to thefabrication equipment which then manufactures the cables according tothe production schedule established by the scheduler 340.

Alternatively, the SMI 375 may also transfer electrical interconnectinformation, including module and pin locations as well as otherrelevant board restrictions and layout information to a printed circuitboard ("PCB") computer aided design ("CAD") system. The PCB CAD systemmay generate PCB fabrication information which will in turn bedownloaded to a routing center for fabricating the PCBs.

The production scheduler 340 will not release a part or module to bebuilt on the line until all of the required parts are available. Whenall parts for a system have been manufactured by, or delivered to, themodule line 350 and system line 360 and are ready for assembly, a kit ofthe parts is delivered to the (automated or manual) system assembly area370 for final assembly.

In the case of manual assembly, the CIM system may display pictorialassembly instructions for each power supply as it passes through anassembly station on video display monitors in assembly area 370 (asshown in FIG. 24 and discussed in greater detail below). The videodisplay files are generated by the SMI 375. The assembly instructionscould be presented in a 3-D format or combined with 3-D views of thepower supply. In the case of automated assembly, the machine readableassembly instructions are delivered to the assembly area 370 instead ofthe video display instructions.

The completed system is then tested according to the test protocolcreated by the SMI 375, and if specified by the customer, burn-in andspecial environmental screening is also performed. The completed systemis shipped to the customer after it passes all of the tests.

An example of a computer integrated manufacturing "CIM" system assemblyarea is shown in FIG. 24. A computer screen 701A displays customer orderinformation provided by the CIM system at a part kitting station 701enabling the operator to collect the necessary components to build thesystem. The SMI provides this information for each order to CRT 701A. Atmicroprocessor programming station 702, the programmable devices for thefront-end board are programmed using programming specifications 702Aprovided by the SMI. The modules, mounting plate, and heatsinks areassembled together at station 703. Bill-of-material and assembly drawinginformation 703A generated by the SMI are displayed on a CRT nearstation 703 by the CIM system for reference by the operator. Theprogrammed device is assembled to the front end at station 704 withreference to the assembly drawing displayed at CRT 704A.

The internal wiring is fabricated at station 705 as explained above inconnection with the snake wiring system and FIG. 15 using specificationsprovided by the SMI. At stations 706 and 708 the PCBs and cables areassembled onto the modules and mounting plate assembly using theassembly drawing and cable run list information displayed at CRT 706A.

Label specifications 709A are provided to a label station 709 where theappropriate labels are affixed to the PPU with reference to the assemblydrawing displayed at CRT 709B. Labels may be printed or laser-generatedon the fly or selected from preprinted stock using the labelspecifications 709A generated by the SMI. Afterward, the PPU is testedat the high potential ("Hi-Pot") and automatic test equipment ("ATE")test station 710. Test specifications for the PPU may be provided to thetest equipment and the operator protocol may be displayed on a CRT 710Aby the SMI as shown in FIG. 24. After testing the HUBs and connectingcable assemblies are introduced at station 711. Assembly drawings andshipping information are displayed on CRT 711a. Product documentationand the assembled PPU are then packaged and sent to shipping 712 fordelivery to the customer.

The above system allows for reductions in the lead time from design tomanufacture of custom power supplies. Using the above-described powersupply design system in conjunction with the automated manufacturing ofDC-DC converters and other power system sub-assemblies allows powersupply manufacturers to ship custom power supplies within a day or twoafter the specification is complete. A user, such as a power supplydesign engineer located at a customer's plant, may design a completecustom power supply and have the manufactured unit shipped by themanufacturer within days of determining the specifications for the powersupply. The above system therefore allows for drastic reduction of thetypical several-month-long cycle from specification to design throughmanufacture that is currently typical in the industry.

In an alternative embodiment, the module design process may be skippedat block 284 (FIG. 8) and a local algorithm may be used to estimate thespecifications and packages for the required complement of DC-DCconverter modules. This complement of modules would then be used toallow the mechanical, thermal, and options design to be completed. Thedetailed designs for each of the converter modules would not begenerated by the remote module designer 192 (FIG. 5) until the completedsystem design is sent by the user to the remote computer at step 289 inFIG. 8. Criteria for determining package size based upon deliverablepower requirements may be stored (e.g., as tables or algorithms) in theComponent Selection Criteria Database 122. After the converter packageoutlines are estimated the mechanical layout can be performed by theuser. This saves time and allows remote users, without modems, to createfirst-pass designs.

The local system 110 determines the sizes and quantities of DC-DCconverter modules required to deliver each specified output voltagebased upon specified output power requirements. In general, the amountof power which can be delivered from a particular size DC-DC converterpackage (e.g., 10, 20, 30, FIG. 1) is a function of output voltage,converter DC input voltage range and maximum baseplate operatingtemperature. The DC input voltage range for the DC-DC converter modulesin the power system 40 may be determined from the input and outputspecifications. The AC input voltage range and the type of front-endselected will each affect the range of DC voltage input to the DC-DCconverter modules. The maximum baseplate temperature specified by theuser will be used for the calculation.

Alternatively, the amount of power which can be delivered from eachmodule package size at a particular output voltage can be closelyapproximated using a look-up table in the selection criteria database122. The power level for each package size is calculated. For example,at a maximum baseplate temperature of 100 degrees C and a DC inputvoltage operating range of 275 to 425 VDC (which conforms to the outputvoltage range of a power factor correcting front-end module), the maximodule package 30 in FIG. 1 can typically deliver a maximum of 100Amperes of current (limited by current carrying capacity of output pins36) at output voltages up to 3.3 Volts; 400 Watts at 5 Volts output; 500Watts at 15 Volt output; and 600 Watts for output voltages above 24Volts. Maximum deliverable power at voltages between 3.3 and 24 Voltscan be inferred by linear interpolation (or on the basis of additionaltable entries or algorithms). Similar current limitation and powerlimitation rules apply to the mini 20 and micro 10 module packages andoutput pin styles shown in FIG. 1.

Other embodiments are within the scope of the following claims.

What is claimed is:
 1. An automated power supply design system foraiding a user to design a custom power supply to be fabricated by apredetermined fabrication facility characterized by a predefined set oftools and processes, the design system comprising:informationrepresenting predetermined limitations which, if observed, ensure thatsaid custom power supply can be fabricated using said predefined set oftools and processes; an interface for receiving power supplyspecifications from said user; a component definition feature having aninput for receiving said power supply specifications, said componentdefinition feature generating a complement of components based upon saidpower supply specifications and providing mechanical parameters for saidcomponents; a mechanical layout feature having an input for receivingsaid mechanical parameters and an input for receiving said power supplyspecifications from said user, said system generating a mechanicaldesign of said custom power supply constrained using said information,said system preventing generation of a design that requires tools orprocesses other than the predefined set of tools and processes.
 2. Theautomated power supply design system of claim 1 further comprising:anautomated manufacturing specifications generator for providingmanufacturing specifications needed by said manufacturing system tomanufacture said custom power supply.
 3. The automated power supplydesign system of claim 2 wherein said automated manufacturingspecifications generator supplies specifications for manufacturingcables for said custom power supply.
 4. The automated power supplydesign system of claim 2 wherein said automated manufacturingspecifications generator supplies specifications for manufacturing amounting plate for said custom power supply.
 5. The automated powersupply design system of claim 2 wherein said automated manufacturingspecifications generator supplies specifications for manufacturingheatsinks for said custom power supply.
 6. The automated power supplydesign system of claim 2 wherein said automated manufacturingspecifications generator supplies specifications for manufacturingelectrical power converter modules for said custom power supply.
 7. Theautomated power supply design system of claim 2 wherein said automatedmanufacturing specifications generator supplies specifications formanufacturing front-end assemblies for said custom power supply.
 8. Theautomated power supply design system of claim 7 wherein said automatedmanufacturing specifications generator supplies specifications forprogramming a programmable memory device with output controlinformation.
 9. The automated power supply design system of claim 2further comprising:a computer integrated manufacturing ("CIM") facilityincluding at least one fabrication station for manufacturing at leastone component for said custom power supply, said CIM facility having aninput for receiving component specifications comprising selected ones ofsaid manufacturing specifications.
 10. The automated power supply designsystem of claim 9 further comprising:a production scheduler connected toreceive said component specifications and to allocate a time slot forproduction of said at least one component by said CIM facility.
 11. Theautomated power supply design system of claim 9 wherein said CIMfacility further comprises:a wiring station having an input forreceiving interconnection specifications for fabricating interconnectioncomponents.
 12. The automated power supply design system of claim 11wherein said interconnection specifications are for a circuit board andsaid wiring station fabricates circuit boards.
 13. The automated powersupply design system of claim 11 wherein said interconnectionspecifications are for a wiring harness and said wiring stationfabricates wiring harnesses.
 14. The automated power supply designsystem of claim 13 wherein said wiring harness comprises a flatmulti-conductor cable element and at least two tap elements and saidinterconnection specifications include at least a length and a taplocation specification.
 15. The automated power supply design system ofclaim 14 wherein said interconnection specifications further comprisefold and bend location specifications.
 16. The automated power supplydesign system of claim 10 wherein said CIM facility further comprises:aheatsink station having an input for receiving heatsink specifications.17. The automated power supply design system of claim 16 wherein saidheatsink specifications comprise machining instructions and saidheatsink station comprises machining equipment for fabricating aheatsink from metal stock.
 18. The automated power supply design systemof claim 16 wherein said heatsink specifications comprise positioninformation and instructions for selecting and installing prefabricatedheatsink components.
 19. The automated power supply design system ofclaim 1 wherein said information comprises at least one of the followingcharacteristics:(a) a limitation imposed by too ling restrictions of amanufacturing line; (b) a minimum component spacing limitation imposedto allow for wiring components; or (c) a component orientationlimitation.
 20. The automated power supply design system of claim 1wherein said power supply specifications further comprises power supplyinput specifications and output specifications and said interfaceaccepts numerical entries.
 21. The automated power supply design systemof claim 20 wherein said interface further comprises a layout feature inwhich component locations may be defined in a virtual space.
 22. Theautomated power supply design system of claim 21 wherein said layoutfeature further comprises component icons representative of saidcomplement of components and said icons may be moved around said virtualspace to define said component locations.
 23. The automated power supplydesign system of claim 22 wherein said layout feature further comprisesa feature allowing the user to manipulate the size or shape of saidvirtual space.
 24. The automated power supply design system of claim 22wherein said layout feature further comprises a drawing feature in whichsaid system automatically adjusts said virtual space to fit anarrangement of said component icons.
 25. The automated power supplydesign system of claim 24 wherein said arrangement is created by saiduser.
 26. The automated power supply design system of claim 22 whereinsaid layout feature further comprises an automatic arrangement featurein which said system automatically arranges said component icons andcreates said virtual space to fit said arrangement of said componenticons.
 27. The automated power supply design system of claim 21, 22, 23,24, 25, or 26 wherein said virtual space comprises a flat surface. 28.The automated power supply design system of claim 21, 22, 23, 24, 25, or26 wherein said virtual space comprises at least two separate flatsurfaces.
 29. The automated power supply design system of claim 21, 22,23, 24, 25, or 26 wherein said component locations and said virtualspace define the mechanical specifications for said custom power supply,including a mounting surface and mounting features.
 30. The automatedpower supply design system of claim 20 wherein said power supplyspecifications further comprise thermal specifications.
 31. Theautomated power supply design system of claim 20 wherein said powersupply specifications further comprise safety agency specifications. 32.The automated power supply design system of claim 20 wherein said powersupply specifications further comprise information about the timing ofturning on or off at least one output.
 33. The automated power supplydesign system of claim 20 wherein said power supply specificationsfurther comprise information about the sequence for turning on or off atleast two outputs.
 34. The automated power supply design system of claim20 wherein said power supply specifications further comprise informationregarding at least one of the following:(a) an output voltage, (b) anoutput power, (c) a current limiting set point, (d) an over voltage setpoint, (e) output ripple, (f) input voltage range, or (g) a noise level.35. The automated power supply design system of claim 1 wherein saidpower supply specifications further comprise power supply inputspecifications and output specifications and said interface provides alist of choices for at least one input specification.
 36. The automatedpower supply design system of claim 35 wherein said list of choicesfurther comprises button selectable options.
 37. The automated powersupply design system of claim 35 wherein said list of choices furthercomprises a pull-down list of options.
 38. The automated power supplydesign system of claim 1 wherein said complement of components furthercomprises an electrical power converter module and said system generatesan electrical design for said electrical power converter module.
 39. Theautomated power supply design system of claim 38 wherein said systemcalculates an efficiency for said electrical power converter module. 40.The automated power supply design system of claim 38 wherein said systemgenerates an electrical design which is optimized with respect to aoptimization parameter such as efficiency, reliability, or cost.
 41. Theautomated power supply design system of claim 40 wherein two or more ofsaid optimization parameters are assigned relative weights and saidsystem generates said electrical design optimizing said optimizationparameters according to assigned relative weights.
 42. The automatedpower supply design system of claim 1 wherein said complement ofcomponents further comprises a plurality of electrical power convertermodules and said system generates an electrical design for each of saidelectrical power converter modules and provides an efficiency rating foreach of said electrical power converter modules;said system calculatesthe total input power required by said electrical power convertermodules using said efficiency ratings and the power output of saidcustom power supply, and selects circuitry for a front-end assembly. 43.The automated power supply design system of claim 42 wherein said systemfurther calculates a total power dissipation of said custom power supplyand calculates at least one heatsink dimension.
 44. The automated powersupply design system of claim 1 wherein said system provides feasibilityinformation to said user regarding at least one of the followingconditions:(a) cooling requirements; (b) heatsink dimensions; (c)component orientation; (d) component spacing; (e) safety agencyrequirements; or (f) output orientation.
 45. The automated power supplydesign system of claim 1 wherein said custom power supply furthercomprises a user-defined package and said specifications furthercomprise at least one of the following details:(a) a shape of saiduser-defined package; (b) a dimension of said user-defined package; (c)a position of at least one of said components in said user-definedpackage; (d) an orientation of at least one of said components in saiduser-defined package.
 46. The automated power supply design system ofclaim 1 wherein said system provides feasibility information to saiduser, said feasibility information comprising acceptable relativelocations and orientations for said components.
 47. The automated powersupply design system of claim 1 wherein said information comprises atleast one of the following:(a) safety agency specifications; (b)limitations imposed to allow two or more power converters to beconnected into a load sharing array; or (c) thermal constraints.
 48. Theautomated power supply design system of claim 1 wherein said complementof components comprises electrical power converter modules.
 49. Theautomated power supply design system of claim 1 wherein said complementof components comprises a front end module.
 50. An automated powersupply design system for aiding a user to design a custom power supplyto be manufactured by a predetermined manufacturing system characterizedby a predefined set of tools and processes, the design systemcomprising:information representing predetermined limitations which, ifobserved, ensure that said custom power supply can be fabricated usingsaid predefined set of tools and processes; an interface for receivingpower supply specifications from said user; a component definitionfeature having an input for receiving said power supply specifications,said component definition feature generating a complement of componentsbased on said power supply specifications; said power supply designsystem generating a custom power supply design for said custom powersupply constrained using said information, said system preventinggeneration of a design that requires tools or processes other than thepredefined set of tools and processes; and an automated manufacturingspecifications generator having an input for receiving said custom powersupply design and supplying manufacturing specifications needed by saidmanufacturing system to manufacture said custom power supply.
 51. Amethod for aiding a user to design a custom power supply to bemanufactured by a predetermined manufacturing system characterized by apredefined set of tools and processes, the method comprising:receivingspecifications from said user; generating a complement of components;providing mechanical parameters for said components; collecting, fromsaid user, mechanical design information for said custom power supply;generating a design for said custom power supply constrained usinginformation representing predetermined limitations which, if observed,ensure that said custom power supply can be manufactured using saidpredefined tools and processes, said method preventing generation of adesign that requires tools or processes other than the predefined set oftools and processes.
 52. The method of claim 51 furthercomprising:generating manufacturing specifications needed by saidmanufacturing system to manufacture said custom power supply.
 53. Themethod of claim 52 wherein said manufacturing specifications furthercomprise at least one of the following:(a) specifications formanufacturing cables for said custom power supply; (b) specificationsfor manufacturing a mounting plate for said custom power supply; (c)specifications for manufacturing heatsinks for said custom power supply;(d) specifications for manufacturing electrical power converter modulesfor said custom power supply; (e) specifications for manufacturingfront-end assemblies for said custom power supply; or (f) specificationsfor programming a programmable memory device with output controlinformation.
 54. The method of claim 52 further comprising:providing acustom power supply design to a computer integrated manufacturing("CIM") facility including at least one fabrication station forautomatically manufacturing at least one component for said custom powersupply.
 55. The method of claim 51 wherein said information comprises atleast one of the following characteristics:(a) a limitation imposed bytooling restrictions of a manufacturing line; (b) a minimum componentspacing limitation imposed to allow for wiring components; or (c) acomponent orientation limitation.
 56. The method of claim 51 furthercomprising:providing a layout feature allowing component locations to bedefined within a virtual space.
 57. The method of claim 56 furthercomprising:providing component icons representative of said complementof components; and allowing said user to move said icons in said virtualspace to define said component locations.
 58. The method of claim 56further comprising automatically arranging said component locations andadjusting said virtual space to fit said arrangement of said componentlocations.
 59. The method of claim 51 wherein said complement ofcomponents further comprises an electrical power converter module andsaid method further comprises generating an electrical design for saidelectrical power converter module.
 60. The method of claim 51 whereinsaid complement of components further comprises a plurality ofelectrical power converter modules and said method furthercomprises:generating an electrical design for each of said electricalpower converter modules and provides an efficiency rating for each ofsaid electrical power converter modules; calculating the total inputpower required by said electrical power converter modules using saidefficiency ratings and the power output of said custom power supply; andselecting circuitry for a front-end assembly.
 61. The method of claim 60further comprising calculating a total power dissipation of said custompower supply and calculating at least one heatsink dimension.
 62. Themethod of claim 51 further comprising providing feasibility informationto said user regarding at least one of the following conditions:(a)cooling requirements; (b) heatsink dimensions; (c) componentorientation; (d) component spacing; (e) safety agency requirements; or(f) output orientation.
 63. A method for aiding a user to design acustom power supply to be manufactured by a predetermined manufacturingsystem characterized by a predefined set of tools and processes, themethod comprising:receiving specifications from said user; generating acomplement of components based upon said specifications; generating adesign for said custom power supply constrained using informationrepresenting predetermined limitations which, if observed, ensure thatsaid custom power supply can be manufactured using said predefined setof tools and processes, said method preventing generation of a designthat requires tools or processes other than the predefined set of toolsand processes; and generating manufacturing specifications needed bysaid manufacturing system to manufacture said custom power supply.
 64. Acapacitor assembly for use with a power supply, comprisinga capacitor; awiring harness electrically connected to the capacitor and adapted forelectrical connection with the power supply; a mounting assembly formechanically supporting the capacitor and adapted to allow the capacitorassembly to be thermally decoupled from the power supply.
 65. A powersupply, comprising:a plurality of heat dissipative components; and acapacitor assembly adapted for electrical connection with the powersupply and adapted for mounting separate from the heat dissipativecomponents in an environment thermally remote from said heat dissipativecomponents.
 66. A power supply, comprising:a plurality of electricalpower converter modules; a flat multiconductor cable comprising acontrol line for each electrical power converter module, a powerdistribution line, and an auxiliary conductor for connecting adjacentmodules in a load sharing array, said auxiliary conductor including atleast one discontinuity to interrupt electrical connection betweenadjacent electrical power converter modules which are not members of thesame load sharing array.
 67. An automated power supply design system foraiding a user to design a custom power supply to be fabricated by apredefined set of tools and processes, comprising:informationrepresenting predetermined limitations which, if observed, ensure thatsaid custom power supply can be fabricated using said predefined set oftools and processes; an input for receiving power supply specifications;a design engine for generating a complement of components based upon thepower supply specifications, mechanical parameters for said components,and a mechanical design of said custom power supply constrained usingsaid information, said system preventing generation of a design thatrequires tools or processes other than the predefined set of tools andprocesses.
 68. The system of claim 67 wherein the system provides theuser with a variety of possibilities for the mechanical design and theuser is allowed to make choices about the mechanical layout throughinteraction with the system.